Mojo: Add a platform interface for shared memory (embedder::PlatformSharedBuffer).

Make the existing RawSharedBuffer an implementation of that. Later,
we'll plumb in a "PlatformSupport" that'll produce these things, but for
now keep the (static) creation methods where they are.

R=darin@chromium.org

Review URL: https://codereview.chromium.org/471773002

Cr-Commit-Position: refs/heads/master@{#289667}
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@289667 0039d316-1c4b-4281-b951-d872f2087c98

mojo/embedder/platform_shared_buffer.h

+// Copyright 2014 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef MOJO_EMBEDDER_PLATFORM_SHARED_BUFFER_H_
+#define MOJO_EMBEDDER_PLATFORM_SHARED_BUFFER_H_
+
+#include <stddef.h>
+
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "mojo/embedder/scoped_platform_handle.h"
+#include "mojo/system/system_impl_export.h"
+
+namespace mojo {
+namespace embedder {
+
+class PlatformSharedBufferMapping;
+
+// |PlatformSharedBuffer| is an interface for a thread-safe, ref-counted wrapper
+// around OS-specific shared memory. It has the following features:
+//   - A |PlatformSharedBuffer| simply represents a piece of shared memory that
+//     *may* be mapped and *may* be shared to another process.
+//   - A single |PlatformSharedBuffer| may be mapped multiple times. The
+//     lifetime of the mapping (owned by |PlatformSharedBufferMapping|) is
+//     separate from the lifetime of the |PlatformSharedBuffer|.
+//   - Sizes/offsets (of the shared memory and mappings) are arbitrary, and not
+//     restricted by page size. However, more memory may actually be mapped than
+//     requested.
+//
+// It currently does NOT support the following:
+//   - Sharing read-only. (This will probably eventually be supported.)
+//
+// TODO(vtl): Rectify this with |base::SharedMemory|.
+class MOJO_SYSTEM_IMPL_EXPORT PlatformSharedBuffer
+    : public base::RefCountedThreadSafe<PlatformSharedBuffer> {
+ public:
+  // Gets the size of shared buffer (in number of bytes).
+  virtual size_t GetNumBytes() const = 0;
+
+  // Maps (some) of the shared buffer into memory; [|offset|, |offset + length|]
+  // must be contained in [0, |num_bytes|], and |length| must be at least 1.
+  // Returns null on failure.
+  virtual scoped_ptr<PlatformSharedBufferMapping> Map(size_t offset,
+                                                      size_t length) = 0;
+
+  // Checks if |offset| and |length| are valid arguments.
+  virtual bool IsValidMap(size_t offset, size_t length) = 0;
+
+  // Like |Map()|, but doesn't check its arguments (which should have been
+  // preflighted using |IsValidMap()|).
+  virtual scoped_ptr<PlatformSharedBufferMapping> MapNoCheck(size_t offset,
+                                                             size_t length) = 0;
+
+  // Duplicates the underlying platform handle and passes it to the caller.
+  // TODO(vtl): On POSIX, we'll need two FDs to support sharing read-only.
+  virtual ScopedPlatformHandle DuplicatePlatformHandle() = 0;
+
+  // Passes the underlying platform handle to the caller. This should only be
+  // called if there's a unique reference to this object (owned by the caller).
+  // After calling this, this object should no longer be used, but should only
+  // be disposed of.
+  virtual ScopedPlatformHandle PassPlatformHandle() = 0;
+
+ protected:
+  friend class base::RefCountedThreadSafe<PlatformSharedBuffer>;
+
+  PlatformSharedBuffer() {}
+  virtual ~PlatformSharedBuffer() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PlatformSharedBuffer);
+};
+
+// An interface for a mapping of a |PlatformSharedBuffer| (compararable to a
+// "file view" in Windows); see above. Created by (implementations of)
+// |PlatformSharedBuffer::Map()|. Automatically unmaps memory on destruction.
+//
+// Mappings are NOT thread-safe.
+//
+// Note: This is an entirely separate class (instead of
+// |PlatformSharedBuffer::Mapping|) so that it can be forward-declared.
+class MOJO_SYSTEM_IMPL_EXPORT PlatformSharedBufferMapping {
+ public:
+  // IMPORTANT: Implementations must implement a destructor that unmaps memory.
+  virtual ~PlatformSharedBufferMapping() {}
+
+  virtual void* GetBase() const = 0;
+  virtual size_t GetLength() const = 0;
+
+ protected:
+  PlatformSharedBufferMapping() {}
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(PlatformSharedBufferMapping);
+};
+
+}  // namespace embedder
+}  // namespace mojo
+
+#endif  // MOJO_EMBEDDER_PLATFORM_SHARED_BUFFER_H_

mojo/mojo_base.gyp

@@ -108,6 +108,7 @@
         'embedder/platform_handle_utils_posix.cc',
         'embedder/platform_handle_utils_win.cc',
         'embedder/platform_handle_vector.h',
+        'embedder/platform_shared_buffer.h',
         'embedder/scoped_platform_handle.h',
         'system/channel.cc',
         'system/channel.h',

mojo/system/core.cc

@@ -8,6 +8,7 @@
 
 #include "base/logging.h"
 #include "base/time/time.h"
+#include "mojo/embedder/platform_shared_buffer.h"
 #include "mojo/public/c/system/macros.h"
 #include "mojo/system/constants.h"
 #include "mojo/system/data_pipe.h"
@@ -19,7 +20,6 @@
 #include "mojo/system/memory.h"
 #include "mojo/system/message_pipe.h"
 #include "mojo/system/message_pipe_dispatcher.h"
-#include "mojo/system/raw_shared_buffer.h"
 #include "mojo/system/shared_buffer_dispatcher.h"
 #include "mojo/system/waiter.h"
 
@@ -516,13 +516,13 @@ MojoResult Core::MapBuffer(MojoHandle buffer_handle,
   if (!dispatcher)
     return MOJO_RESULT_INVALID_ARGUMENT;
 
-  scoped_ptr<RawSharedBufferMapping> mapping;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping;
   MojoResult result = dispatcher->MapBuffer(offset, num_bytes, flags, &mapping);
   if (result != MOJO_RESULT_OK)
     return result;
 
   DCHECK(mapping);
-  void* address = mapping->base();
+  void* address = mapping->GetBase();
   {
     base::AutoLock locker(mapping_table_lock_);
     result = mapping_table_.AddMapping(mapping.Pass());

mojo/system/dispatcher.cc

@@ -199,10 +199,11 @@ MojoResult Dispatcher::DuplicateBufferHandle(
   return DuplicateBufferHandleImplNoLock(options, new_dispatcher);
 }
 
-MojoResult Dispatcher::MapBuffer(uint64_t offset,
+MojoResult Dispatcher::MapBuffer(
+    uint64_t offset,
     uint64_t num_bytes,
     MojoMapBufferFlags flags,
-                                 scoped_ptr<RawSharedBufferMapping>* mapping) {
+    scoped_ptr<embedder::PlatformSharedBufferMapping>* mapping) {
   base::AutoLock locker(lock_);
   if (is_closed_)
     return MOJO_RESULT_INVALID_ARGUMENT;
@@ -353,7 +354,7 @@ MojoResult Dispatcher::MapBufferImplNoLock(
     uint64_t /*offset*/,
     uint64_t /*num_bytes*/,
     MojoMapBufferFlags /*flags*/,
-    scoped_ptr<RawSharedBufferMapping>* /*mapping*/) {
+    scoped_ptr<embedder::PlatformSharedBufferMapping>* /*mapping*/) {
   lock_.AssertAcquired();
   DCHECK(!is_closed_);
   // By default, not supported. Only needed for buffer dispatchers.

mojo/system/dispatcher.h

@@ -25,6 +25,11 @@
 #include "mojo/system/system_impl_export.h"
 
 namespace mojo {
+
+namespace embedder {
+class PlatformSharedBufferMapping;
+}
+
 namespace system {
 
 class Channel;
@@ -34,7 +39,6 @@ class DispatcherTransport;
 class HandleTable;
 class LocalMessagePipeEndpoint;
 class ProxyMessagePipeEndpoint;
-class RawSharedBufferMapping;
 class TransportData;
 class Waiter;
 
@@ -113,10 +117,11 @@ class MOJO_SYSTEM_IMPL_EXPORT Dispatcher
   MojoResult DuplicateBufferHandle(
       UserPointer<const MojoDuplicateBufferHandleOptions> options,
       scoped_refptr<Dispatcher>* new_dispatcher);
-  MojoResult MapBuffer(uint64_t offset,
+  MojoResult MapBuffer(
+      uint64_t offset,
       uint64_t num_bytes,
       MojoMapBufferFlags flags,
-                       scoped_ptr<RawSharedBufferMapping>* mapping);
+      scoped_ptr<embedder::PlatformSharedBufferMapping>* mapping);
 
   // Gets the current handle signals state. (The default implementation simply
   // returns a default-constructed |HandleSignalsState|, i.e., no signals
@@ -260,7 +265,7 @@ class MOJO_SYSTEM_IMPL_EXPORT Dispatcher
       uint64_t offset,
       uint64_t num_bytes,
       MojoMapBufferFlags flags,
-      scoped_ptr<RawSharedBufferMapping>* mapping);
+      scoped_ptr<embedder::PlatformSharedBufferMapping>* mapping);
   virtual HandleSignalsState GetHandleSignalsStateImplNoLock() const;
   virtual MojoResult AddWaiterImplNoLock(Waiter* waiter,
                                          MojoHandleSignals signals,

mojo/system/dispatcher_unittest.cc

@@ -9,8 +9,8 @@
 #include "base/memory/scoped_vector.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/simple_thread.h"
+#include "mojo/embedder/platform_shared_buffer.h"
 #include "mojo/system/memory.h"
-#include "mojo/system/raw_shared_buffer.h"
 #include "mojo/system/waiter.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -223,7 +223,7 @@ class ThreadSafetyStressThread : public base::SimpleThread {
         break;
       }
       case MAP_BUFFER: {
-        scoped_ptr<RawSharedBufferMapping> unused;
+        scoped_ptr<embedder::PlatformSharedBufferMapping> unused;
         EXPECT_EQ(
             MOJO_RESULT_INVALID_ARGUMENT,
             dispatcher_->MapBuffer(0u, 0u, MOJO_MAP_BUFFER_FLAG_NONE, &unused));

mojo/system/mapping_table.cc

@@ -5,8 +5,8 @@
 #include "mojo/system/mapping_table.h"
 
 #include "base/logging.h"
+#include "mojo/embedder/platform_shared_buffer.h"
 #include "mojo/system/constants.h"
-#include "mojo/system/raw_shared_buffer.h"
 
 namespace mojo {
 namespace system {
@@ -20,13 +20,13 @@ MappingTable::~MappingTable() {
 }
 
 MojoResult MappingTable::AddMapping(
-    scoped_ptr<RawSharedBufferMapping> mapping) {
+    scoped_ptr<embedder::PlatformSharedBufferMapping> mapping) {
   DCHECK(mapping);
 
   if (address_to_mapping_map_.size() >= kMaxMappingTableSize)
     return MOJO_RESULT_RESOURCE_EXHAUSTED;
 
-  uintptr_t address = reinterpret_cast<uintptr_t>(mapping->base());
+  uintptr_t address = reinterpret_cast<uintptr_t>(mapping->GetBase());
   DCHECK(address_to_mapping_map_.find(address) ==
          address_to_mapping_map_.end());
   address_to_mapping_map_[address] = mapping.release();
@@ -37,7 +37,7 @@ MojoResult MappingTable::RemoveMapping(uintptr_t address) {
   AddressToMappingMap::iterator it = address_to_mapping_map_.find(address);
   if (it == address_to_mapping_map_.end())
     return MOJO_RESULT_INVALID_ARGUMENT;
-  RawSharedBufferMapping* mapping_to_delete = it->second;
+  embedder::PlatformSharedBufferMapping* mapping_to_delete = it->second;
   address_to_mapping_map_.erase(it);
   delete mapping_to_delete;
   return MOJO_RESULT_OK;

mojo/system/mapping_table.h

@@ -16,10 +16,14 @@
 #include "mojo/system/system_impl_export.h"
 
 namespace mojo {
+
+namespace embedder {
+class PlatformSharedBufferMapping;
+}
+
 namespace system {
 
 class Core;
-class RawSharedBufferMapping;
 
 // Test-only function (defined/used in embedder/test_embedder.cc). Declared here
 // so it can be friended.
@@ -28,7 +32,7 @@ bool ShutdownCheckNoLeaks(Core*);
 }
 
 // This class provides the (global) table of memory mappings (owned by |Core|),
-// which maps mapping base addresses to |RawSharedBuffer::Mapping|s.
+// which maps mapping base addresses to |PlatformSharedBufferMapping|s.
 //
 // This class is NOT thread-safe; locking is left to |Core|.
 class MOJO_SYSTEM_IMPL_EXPORT MappingTable {
@@ -38,13 +42,14 @@ class MOJO_SYSTEM_IMPL_EXPORT MappingTable {
 
   // Tries to add a mapping. (Takes ownership of the mapping in all cases; on
   // failure, it will be destroyed.)
-  MojoResult AddMapping(scoped_ptr<RawSharedBufferMapping> mapping);
+  MojoResult AddMapping(
+      scoped_ptr<embedder::PlatformSharedBufferMapping> mapping);
   MojoResult RemoveMapping(uintptr_t address);
 
  private:
   friend bool internal::ShutdownCheckNoLeaks(Core*);
 
-  typedef base::hash_map<uintptr_t, RawSharedBufferMapping*>
+  typedef base::hash_map<uintptr_t, embedder::PlatformSharedBufferMapping*>
       AddressToMappingMap;
   AddressToMappingMap address_to_mapping_map_;
 

mojo/system/multiprocess_message_pipe_unittest.cc

@@ -21,6 +21,7 @@
 #include "build/build_config.h"              // TODO(vtl): Remove this.
 #include "mojo/common/test/multiprocess_test_helper.h"
 #include "mojo/common/test/test_utils.h"
+#include "mojo/embedder/platform_shared_buffer.h"
 #include "mojo/embedder/scoped_platform_handle.h"
 #include "mojo/system/channel.h"
 #include "mojo/system/dispatcher.h"
@@ -29,7 +30,6 @@
 #include "mojo/system/platform_handle_dispatcher.h"
 #include "mojo/system/proxy_message_pipe_endpoint.h"
 #include "mojo/system/raw_channel.h"
-#include "mojo/system/raw_shared_buffer.h"
 #include "mojo/system/shared_buffer_dispatcher.h"
 #include "mojo/system/test_utils.h"
 #include "mojo/system/waiter.h"
@@ -358,16 +358,16 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckSharedBuffer) {
       static_cast<SharedBufferDispatcher*>(dispatchers[0].get()));
 
   // Make a mapping.
-  scoped_ptr<RawSharedBufferMapping> mapping;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping;
   CHECK_EQ(dispatcher->MapBuffer(0, 100, MOJO_MAP_BUFFER_FLAG_NONE, &mapping),
            MOJO_RESULT_OK);
   CHECK(mapping);
-  CHECK(mapping->base());
-  CHECK_EQ(mapping->length(), 100u);
+  CHECK(mapping->GetBase());
+  CHECK_EQ(mapping->GetLength(), 100u);
 
   // Write some stuff to the shared buffer.
   static const char kHello[] = "hello";
-  memcpy(mapping->base(), kHello, sizeof(kHello));
+  memcpy(mapping->GetBase(), kHello, sizeof(kHello));
 
   // We should be able to close the dispatcher now.
   dispatcher->Close();
@@ -404,7 +404,7 @@ MOJO_MULTIPROCESS_TEST_CHILD_MAIN(CheckSharedBuffer) {
 
   // It should have written something to the shared buffer.
   static const char kWorld[] = "world!!!";
-  CHECK_EQ(memcmp(mapping->base(), kWorld, sizeof(kWorld)), 0);
+  CHECK_EQ(memcmp(mapping->GetBase(), kWorld, sizeof(kWorld)), 0);
 
   // And we're done.
   mp->Close(0);
@@ -435,12 +435,12 @@ TEST_F(MultiprocessMessagePipeTest, MAYBE_SharedBufferPassing) {
   ASSERT_TRUE(dispatcher);
 
   // Make a mapping.
-  scoped_ptr<RawSharedBufferMapping> mapping;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping;
   EXPECT_EQ(MOJO_RESULT_OK,
             dispatcher->MapBuffer(0, 100, MOJO_MAP_BUFFER_FLAG_NONE, &mapping));
   ASSERT_TRUE(mapping);
-  ASSERT_TRUE(mapping->base());
-  ASSERT_EQ(100u, mapping->length());
+  ASSERT_TRUE(mapping->GetBase());
+  ASSERT_EQ(100u, mapping->GetLength());
 
   // Send the shared buffer.
   const std::string go1("go 1");
@@ -483,11 +483,11 @@ TEST_F(MultiprocessMessagePipeTest, MAYBE_SharedBufferPassing) {
   // After we get it, the child should have written something to the shared
   // buffer.
   static const char kHello[] = "hello";
-  EXPECT_EQ(0, memcmp(mapping->base(), kHello, sizeof(kHello)));
+  EXPECT_EQ(0, memcmp(mapping->GetBase(), kHello, sizeof(kHello)));
 
   // Now we'll write some stuff to the shared buffer.
   static const char kWorld[] = "world!!!";
-  memcpy(mapping->base(), kWorld, sizeof(kWorld));
+  memcpy(mapping->GetBase(), kWorld, sizeof(kWorld));
 
   // And send a message to signal that we've written stuff.
   const std::string go3("go 3");

mojo/system/raw_shared_buffer.cc

@@ -25,6 +25,7 @@ RawSharedBuffer* RawSharedBuffer::Create(size_t num_bytes) {
   return rv;
 }
 
+// static
 RawSharedBuffer* RawSharedBuffer::CreateFromPlatformHandle(
     size_t num_bytes,
     embedder::ScopedPlatformHandle platform_handle) {
@@ -41,10 +42,15 @@ RawSharedBuffer* RawSharedBuffer::CreateFromPlatformHandle(
   return rv;
 }
 
-scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::Map(size_t offset,
+size_t RawSharedBuffer::GetNumBytes() const {
+  return num_bytes_;
+}
+
+scoped_ptr<embedder::PlatformSharedBufferMapping> RawSharedBuffer::Map(
+    size_t offset,
     size_t length) {
   if (!IsValidMap(offset, length))
-    return scoped_ptr<RawSharedBufferMapping>();
+    return scoped_ptr<embedder::PlatformSharedBufferMapping>();
 
   return MapNoCheck(offset, length);
 }
@@ -61,7 +67,8 @@ bool RawSharedBuffer::IsValidMap(size_t offset, size_t length) {
   return true;
 }
 
-scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::MapNoCheck(size_t offset,
+scoped_ptr<embedder::PlatformSharedBufferMapping> RawSharedBuffer::MapNoCheck(
+    size_t offset,
     size_t length) {
   DCHECK(IsValidMap(offset, length));
   return MapImpl(offset, length);
@@ -82,5 +89,17 @@ RawSharedBuffer::RawSharedBuffer(size_t num_bytes) : num_bytes_(num_bytes) {
 RawSharedBuffer::~RawSharedBuffer() {
 }
 
+RawSharedBufferMapping::~RawSharedBufferMapping() {
+  Unmap();
+}
+
+void* RawSharedBufferMapping::GetBase() const {
+  return base_;
+}
+
+size_t RawSharedBufferMapping::GetLength() const {
+  return length_;
+}
+
 }  // namespace system
 }  // namespace mojo

mojo/system/raw_shared_buffer.h

@@ -8,33 +8,15 @@
 #include <stddef.h>
 
 #include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/memory/scoped_ptr.h"
-#include "mojo/embedder/scoped_platform_handle.h"
+#include "mojo/embedder/platform_shared_buffer.h"
 #include "mojo/system/system_impl_export.h"
 
 namespace mojo {
 namespace system {
 
-class RawSharedBufferMapping;
-
-// |RawSharedBuffer| is a thread-safe, ref-counted wrapper around OS-specific
-// shared memory. It has the following features:
-//   - A |RawSharedBuffer| simply represents a piece of shared memory that *may*
-//     be mapped and *may* be shared to another process.
-//   - A single |RawSharedBuffer| may be mapped multiple times. The lifetime of
-//     the mapping (owned by |RawSharedBufferMapping|) is separate from the
-//     lifetime of the |RawSharedBuffer|.
-//   - Sizes/offsets (of the shared memory and mappings) are arbitrary, and not
-//     restricted by page size. However, more memory may actually be mapped than
-//     requested.
-//
-// It currently does NOT support the following:
-//   - Sharing read-only. (This will probably eventually be supported.)
-//
-// TODO(vtl): Rectify this with |base::SharedMemory|.
+// A simple implementation of |embedder::PlatformSharedBuffer|.
 class MOJO_SYSTEM_IMPL_EXPORT RawSharedBuffer
-    : public base::RefCountedThreadSafe<RawSharedBuffer> {
+    : public embedder::PlatformSharedBuffer {
  public:
   // Creates a shared buffer of size |num_bytes| bytes (initially zero-filled).
   // |num_bytes| must be nonzero. Returns null on failure.
@@ -44,34 +26,21 @@ class MOJO_SYSTEM_IMPL_EXPORT RawSharedBuffer
       size_t num_bytes,
       embedder::ScopedPlatformHandle platform_handle);
 
-  // Maps (some) of the shared buffer into memory; [|offset|, |offset + length|]
-  // must be contained in [0, |num_bytes|], and |length| must be at least 1.
-  // Returns null on failure.
-  scoped_ptr<RawSharedBufferMapping> Map(size_t offset, size_t length);
-
-  // Checks if |offset| and |length| are valid arguments.
-  bool IsValidMap(size_t offset, size_t length);
-
-  // Like |Map()|, but doesn't check its arguments (which should have been
-  // preflighted using |IsValidMap()|).
-  scoped_ptr<RawSharedBufferMapping> MapNoCheck(size_t offset, size_t length);
-
-  // Duplicates the underlying platform handle and passes it to the caller.
-  embedder::ScopedPlatformHandle DuplicatePlatformHandle();
-
-  // Passes the underlying platform handle to the caller. This should only be
-  // called if there's a unique reference to this object (owned by the caller).
-  // After calling this, this object should no longer be used, but should only
-  // be disposed of.
-  embedder::ScopedPlatformHandle PassPlatformHandle();
-
-  size_t num_bytes() const { return num_bytes_; }
+  // |embedder::PlatformSharedBuffer| implementation:
+  virtual size_t GetNumBytes() const OVERRIDE;
+  virtual scoped_ptr<embedder::PlatformSharedBufferMapping> Map(
+      size_t offset,
+      size_t length) OVERRIDE;
+  virtual bool IsValidMap(size_t offset, size_t length) OVERRIDE;
+  virtual scoped_ptr<embedder::PlatformSharedBufferMapping> MapNoCheck(
+      size_t offset,
+      size_t length) OVERRIDE;
+  virtual embedder::ScopedPlatformHandle DuplicatePlatformHandle() OVERRIDE;
+  virtual embedder::ScopedPlatformHandle PassPlatformHandle() OVERRIDE;
 
  private:
-  friend class base::RefCountedThreadSafe<RawSharedBuffer>;
-
   explicit RawSharedBuffer(size_t num_bytes);
-  ~RawSharedBuffer();
+  virtual ~RawSharedBuffer();
 
   // Implemented in raw_shared_buffer_{posix,win}.cc:
 
@@ -84,7 +53,8 @@ class MOJO_SYSTEM_IMPL_EXPORT RawSharedBuffer
   bool InitFromPlatformHandle(embedder::ScopedPlatformHandle platform_handle);
 
   // The platform-dependent part of |Map()|; doesn't check arguments.
-  scoped_ptr<RawSharedBufferMapping> MapImpl(size_t offset, size_t length);
+  scoped_ptr<embedder::PlatformSharedBufferMapping> MapImpl(size_t offset,
+                                                            size_t length);
 
   const size_t num_bytes_;
 
@@ -96,20 +66,15 @@ class MOJO_SYSTEM_IMPL_EXPORT RawSharedBuffer
   DISALLOW_COPY_AND_ASSIGN(RawSharedBuffer);
 };
 
-// A mapping of a |RawSharedBuffer| (compararable to a "file view" in Windows);
-// see above. Created by |RawSharedBuffer::Map()|. Automatically unmaps memory
-// on destruction.
-//
-// Mappings are NOT thread-safe.
-//
-// Note: This is an entirely separate class (instead of
-// |RawSharedBuffer::Mapping|) so that it can be forward-declared.
-class MOJO_SYSTEM_IMPL_EXPORT RawSharedBufferMapping {
+// An implementation of |embedder::PlatformSharedBufferMapping|, produced by
+// |RawSharedBuffer|.
+class MOJO_SYSTEM_IMPL_EXPORT RawSharedBufferMapping
+    : public embedder::PlatformSharedBufferMapping {
  public:
-  ~RawSharedBufferMapping() { Unmap(); }
+  virtual ~RawSharedBufferMapping();
 
-  void* base() const { return base_; }
-  size_t length() const { return length_; }
+  virtual void* GetBase() const OVERRIDE;
+  virtual size_t GetLength() const OVERRIDE;
 
  private:
   friend class RawSharedBuffer;

mojo/system/raw_shared_buffer_posix.cc

@@ -115,7 +115,8 @@ bool RawSharedBuffer::InitFromPlatformHandle(
   return true;
 }
 
-scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::MapImpl(size_t offset,
+scoped_ptr<embedder::PlatformSharedBufferMapping> RawSharedBuffer::MapImpl(
+    size_t offset,
     size_t length) {
   size_t offset_rounding = offset % base::SysInfo::VMAllocationGranularity();
   size_t real_offset = offset - offset_rounding;
@@ -136,11 +137,11 @@ scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::MapImpl(size_t offset,
   // return null either.
   if (real_base == MAP_FAILED || !real_base) {
     PLOG(ERROR) << "mmap";
-    return scoped_ptr<RawSharedBufferMapping>();
+    return scoped_ptr<embedder::PlatformSharedBufferMapping>();
   }
 
   void* base = static_cast<char*>(real_base) + offset_rounding;
-  return make_scoped_ptr(
+  return scoped_ptr<embedder::PlatformSharedBufferMapping>(
       new RawSharedBufferMapping(base, length, real_base, real_length));
 }
 

mojo/system/raw_shared_buffer_unittest.cc

@@ -28,10 +28,11 @@ TEST(RawSharedBufferTest, Basic) {
   // Map it all, scribble some stuff, and then unmap it.
   {
     EXPECT_TRUE(buffer->IsValidMap(0, kNumBytes));
-    scoped_ptr<RawSharedBufferMapping> mapping(buffer->Map(0, kNumBytes));
+    scoped_ptr<embedder::PlatformSharedBufferMapping> mapping(
+        buffer->Map(0, kNumBytes));
     ASSERT_TRUE(mapping);
-    ASSERT_TRUE(mapping->base());
-    int* stuff = static_cast<int*>(mapping->base());
+    ASSERT_TRUE(mapping->GetBase());
+    int* stuff = static_cast<int*>(mapping->GetBase());
     for (size_t i = 0; i < kNumInts; i++)
       stuff[i] = static_cast<int>(i) + kFudge;
   }
@@ -43,19 +44,19 @@ TEST(RawSharedBufferTest, Basic) {
   {
     ASSERT_TRUE(buffer->IsValidMap(0, kNumBytes));
     // Use |MapNoCheck()| this time.
-    scoped_ptr<RawSharedBufferMapping> mapping1(
+    scoped_ptr<embedder::PlatformSharedBufferMapping> mapping1(
         buffer->MapNoCheck(0, kNumBytes));
     ASSERT_TRUE(mapping1);
-    ASSERT_TRUE(mapping1->base());
-    int* stuff1 = static_cast<int*>(mapping1->base());
+    ASSERT_TRUE(mapping1->GetBase());
+    int* stuff1 = static_cast<int*>(mapping1->GetBase());
     for (size_t i = 0; i < kNumInts; i++)
       EXPECT_EQ(static_cast<int>(i) + kFudge, stuff1[i]) << i;
 
-    scoped_ptr<RawSharedBufferMapping> mapping2(
+    scoped_ptr<embedder::PlatformSharedBufferMapping> mapping2(
         buffer->Map((kNumInts / 2) * sizeof(int), 2 * sizeof(int)));
     ASSERT_TRUE(mapping2);
-    ASSERT_TRUE(mapping2->base());
-    int* stuff2 = static_cast<int*>(mapping2->base());
+    ASSERT_TRUE(mapping2->GetBase());
+    int* stuff2 = static_cast<int*>(mapping2->GetBase());
     EXPECT_EQ(static_cast<int>(kNumInts / 2) + kFudge, stuff2[0]);
     EXPECT_EQ(static_cast<int>(kNumInts / 2) + 1 + kFudge, stuff2[1]);
 
@@ -75,11 +76,11 @@ TEST(RawSharedBufferTest, Basic) {
   // it to be.
   {
     EXPECT_TRUE(buffer->IsValidMap(sizeof(int), kNumBytes - sizeof(int)));
-    scoped_ptr<RawSharedBufferMapping> mapping(
+    scoped_ptr<embedder::PlatformSharedBufferMapping> mapping(
         buffer->Map(sizeof(int), kNumBytes - sizeof(int)));
     ASSERT_TRUE(mapping);
-    ASSERT_TRUE(mapping->base());
-    int* stuff = static_cast<int*>(mapping->base());
+    ASSERT_TRUE(mapping->GetBase());
+    int* stuff = static_cast<int*>(mapping->GetBase());
 
     for (size_t j = 0; j < kNumInts - 1; j++) {
       int i = static_cast<int>(j) + 1;
@@ -140,40 +141,43 @@ TEST(RawSharedBufferTest, TooBig) {
 // using the address as the key for unmapping.
 TEST(RawSharedBufferTest, MappingsDistinct) {
   scoped_refptr<RawSharedBuffer> buffer(RawSharedBuffer::Create(100));
-  scoped_ptr<RawSharedBufferMapping> mapping1(buffer->Map(0, 100));
-  scoped_ptr<RawSharedBufferMapping> mapping2(buffer->Map(0, 100));
-  EXPECT_NE(mapping1->base(), mapping2->base());
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping1(
+      buffer->Map(0, 100));
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping2(
+      buffer->Map(0, 100));
+  EXPECT_NE(mapping1->GetBase(), mapping2->GetBase());
 }
 
 TEST(RawSharedBufferTest, BufferZeroInitialized) {
   static const size_t kSizes[] = {10, 100, 1000, 10000, 100000};
   for (size_t i = 0; i < arraysize(kSizes); i++) {
     scoped_refptr<RawSharedBuffer> buffer(RawSharedBuffer::Create(kSizes[i]));
-    scoped_ptr<RawSharedBufferMapping> mapping(buffer->Map(0, kSizes[i]));
+    scoped_ptr<embedder::PlatformSharedBufferMapping> mapping(
+        buffer->Map(0, kSizes[i]));
     for (size_t j = 0; j < kSizes[i]; j++) {
       // "Assert" instead of "expect" so we don't spam the output with thousands
       // of failures if we fail.
-      ASSERT_EQ('\0', static_cast<char*>(mapping->base())[j])
+      ASSERT_EQ('\0', static_cast<char*>(mapping->GetBase())[j])
           << "size " << kSizes[i] << ", offset " << j;
     }
   }
 }
 
 TEST(RawSharedBufferTest, MappingsOutliveBuffer) {
-  scoped_ptr<RawSharedBufferMapping> mapping1;
-  scoped_ptr<RawSharedBufferMapping> mapping2;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping1;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping2;
 
   {
     scoped_refptr<RawSharedBuffer> buffer(RawSharedBuffer::Create(100));
     mapping1 = buffer->Map(0, 100).Pass();
     mapping2 = buffer->Map(50, 50).Pass();
-    static_cast<char*>(mapping1->base())[50] = 'x';
+    static_cast<char*>(mapping1->GetBase())[50] = 'x';
   }
 
-  EXPECT_EQ('x', static_cast<char*>(mapping2->base())[0]);
+  EXPECT_EQ('x', static_cast<char*>(mapping2->GetBase())[0]);
 
-  static_cast<char*>(mapping2->base())[1] = 'y';
-  EXPECT_EQ('y', static_cast<char*>(mapping1->base())[51]);
+  static_cast<char*>(mapping2->GetBase())[1] = 'y';
+  EXPECT_EQ('y', static_cast<char*>(mapping1->GetBase())[51]);
 }
 
 }  // namespace

mojo/system/raw_shared_buffer_win.cc

@@ -57,7 +57,8 @@ bool RawSharedBuffer::InitFromPlatformHandle(
   return false;
 }
 
-scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::MapImpl(size_t offset,
+scoped_ptr<embedder::PlatformSharedBufferMapping> RawSharedBuffer::MapImpl(
+    size_t offset,
     size_t length) {
   size_t offset_rounding = offset % base::SysInfo::VMAllocationGranularity();
   size_t real_offset = offset - offset_rounding;
@@ -75,11 +76,11 @@ scoped_ptr<RawSharedBufferMapping> RawSharedBuffer::MapImpl(size_t offset,
                                   real_length);
   if (!real_base) {
     PLOG(ERROR) << "MapViewOfFile";
-    return scoped_ptr<RawSharedBufferMapping>();
+    return scoped_ptr<embedder::PlatformSharedBufferMapping>();
   }
 
   void* base = static_cast<char*>(real_base) + offset_rounding;
-  return make_scoped_ptr(
+  return scoped_ptr<embedder::PlatformSharedBufferMapping>(
       new RawSharedBufferMapping(base, length, real_base, real_length));
 }
 

mojo/system/remote_message_pipe_unittest.cc

@@ -21,6 +21,7 @@
 #include "build/build_config.h"              // TODO(vtl): Remove this.
 #include "mojo/common/test/test_utils.h"
 #include "mojo/embedder/platform_channel_pair.h"
+#include "mojo/embedder/platform_shared_buffer.h"
 #include "mojo/embedder/scoped_platform_handle.h"
 #include "mojo/system/channel.h"
 #include "mojo/system/local_message_pipe_endpoint.h"
@@ -708,16 +709,16 @@ TEST_F(RemoteMessagePipeTest, MAYBE_SharedBufferPassing) {
   ASSERT_TRUE(dispatcher);
 
   // Make a mapping.
-  scoped_ptr<RawSharedBufferMapping> mapping0;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping0;
   EXPECT_EQ(
       MOJO_RESULT_OK,
       dispatcher->MapBuffer(0, 100, MOJO_MAP_BUFFER_FLAG_NONE, &mapping0));
   ASSERT_TRUE(mapping0);
-  ASSERT_TRUE(mapping0->base());
-  ASSERT_EQ(100u, mapping0->length());
-  static_cast<char*>(mapping0->base())[0] = 'A';
-  static_cast<char*>(mapping0->base())[50] = 'B';
-  static_cast<char*>(mapping0->base())[99] = 'C';
+  ASSERT_TRUE(mapping0->GetBase());
+  ASSERT_EQ(100u, mapping0->GetLength());
+  static_cast<char*>(mapping0->GetBase())[0] = 'A';
+  static_cast<char*>(mapping0->GetBase())[50] = 'B';
+  static_cast<char*>(mapping0->GetBase())[99] = 'C';
 
   // Prepare to wait on MP 1, port 1. (Add the waiter now. Otherwise, if we do
   // it later, it might already be readable.)
@@ -780,27 +781,27 @@ TEST_F(RemoteMessagePipeTest, MAYBE_SharedBufferPassing) {
   dispatcher = static_cast<SharedBufferDispatcher*>(read_dispatchers[0].get());
 
   // Make another mapping.
-  scoped_ptr<RawSharedBufferMapping> mapping1;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping1;
   EXPECT_EQ(
       MOJO_RESULT_OK,
       dispatcher->MapBuffer(0, 100, MOJO_MAP_BUFFER_FLAG_NONE, &mapping1));
   ASSERT_TRUE(mapping1);
-  ASSERT_TRUE(mapping1->base());
-  ASSERT_EQ(100u, mapping1->length());
-  EXPECT_NE(mapping1->base(), mapping0->base());
-  EXPECT_EQ('A', static_cast<char*>(mapping1->base())[0]);
-  EXPECT_EQ('B', static_cast<char*>(mapping1->base())[50]);
-  EXPECT_EQ('C', static_cast<char*>(mapping1->base())[99]);
+  ASSERT_TRUE(mapping1->GetBase());
+  ASSERT_EQ(100u, mapping1->GetLength());
+  EXPECT_NE(mapping1->GetBase(), mapping0->GetBase());
+  EXPECT_EQ('A', static_cast<char*>(mapping1->GetBase())[0]);
+  EXPECT_EQ('B', static_cast<char*>(mapping1->GetBase())[50]);
+  EXPECT_EQ('C', static_cast<char*>(mapping1->GetBase())[99]);
 
   // Write stuff either way.
-  static_cast<char*>(mapping1->base())[1] = 'x';
-  EXPECT_EQ('x', static_cast<char*>(mapping0->base())[1]);
-  static_cast<char*>(mapping0->base())[2] = 'y';
-  EXPECT_EQ('y', static_cast<char*>(mapping1->base())[2]);
+  static_cast<char*>(mapping1->GetBase())[1] = 'x';
+  EXPECT_EQ('x', static_cast<char*>(mapping0->GetBase())[1]);
+  static_cast<char*>(mapping0->GetBase())[2] = 'y';
+  EXPECT_EQ('y', static_cast<char*>(mapping1->GetBase())[2]);
 
   // Kill the first mapping; the second should still be valid.
   mapping0.reset();
-  EXPECT_EQ('A', static_cast<char*>(mapping1->base())[0]);
+  EXPECT_EQ('A', static_cast<char*>(mapping1->GetBase())[0]);
 
   // Close everything that belongs to us.
   mp0->Close(0);
@@ -808,7 +809,7 @@ TEST_F(RemoteMessagePipeTest, MAYBE_SharedBufferPassing) {
   EXPECT_EQ(MOJO_RESULT_OK, dispatcher->Close());
 
   // The second mapping should still be good.
-  EXPECT_EQ('x', static_cast<char*>(mapping1->base())[1]);
+  EXPECT_EQ('x', static_cast<char*>(mapping1->GetBase())[1]);
 }
 
 #if defined(OS_POSIX)

mojo/system/shared_buffer_dispatcher.cc

@@ -70,7 +70,8 @@ MojoResult SharedBufferDispatcher::Create(
   if (num_bytes > kMaxSharedMemoryNumBytes)
     return MOJO_RESULT_RESOURCE_EXHAUSTED;
 
-  scoped_refptr<RawSharedBuffer> shared_buffer(
+  // TODO(vtl): Call out to "platform support" for this.
+  scoped_refptr<embedder::PlatformSharedBuffer> shared_buffer(
       RawSharedBuffer::Create(static_cast<size_t>(num_bytes)));
   if (!shared_buffer)
     return MOJO_RESULT_RESOURCE_EXHAUSTED;
@@ -119,7 +120,7 @@ scoped_refptr<SharedBufferDispatcher> SharedBufferDispatcher::Deserialize(
 
   // Wrapping |platform_handle| in a |ScopedPlatformHandle| means that it'll be
   // closed even if creation fails.
-  scoped_refptr<RawSharedBuffer> shared_buffer(
+  scoped_refptr<embedder::PlatformSharedBuffer> shared_buffer(
       RawSharedBuffer::CreateFromPlatformHandle(
           num_bytes, embedder::ScopedPlatformHandle(platform_handle)));
   if (!shared_buffer) {
@@ -133,7 +134,7 @@ scoped_refptr<SharedBufferDispatcher> SharedBufferDispatcher::Deserialize(
 }
 
 SharedBufferDispatcher::SharedBufferDispatcher(
-    scoped_refptr<RawSharedBuffer> shared_buffer)
+    scoped_refptr<embedder::PlatformSharedBuffer> shared_buffer)
     : shared_buffer_(shared_buffer) {
   DCHECK(shared_buffer_);
 }
@@ -183,7 +184,7 @@ scoped_refptr<Dispatcher>
 SharedBufferDispatcher::CreateEquivalentDispatcherAndCloseImplNoLock() {
   lock().AssertAcquired();
   DCHECK(shared_buffer_);
-  scoped_refptr<RawSharedBuffer> shared_buffer;
+  scoped_refptr<embedder::PlatformSharedBuffer> shared_buffer;
   shared_buffer.swap(shared_buffer_);
   return scoped_refptr<Dispatcher>(new SharedBufferDispatcher(shared_buffer));
 }
@@ -206,7 +207,7 @@ MojoResult SharedBufferDispatcher::MapBufferImplNoLock(
     uint64_t offset,
     uint64_t num_bytes,
     MojoMapBufferFlags flags,
-    scoped_ptr<RawSharedBufferMapping>* mapping) {
+    scoped_ptr<embedder::PlatformSharedBufferMapping>* mapping) {
   lock().AssertAcquired();
   DCHECK(shared_buffer_);
 
@@ -258,7 +259,7 @@ bool SharedBufferDispatcher::EndSerializeAndCloseImplNoLock(
     return false;
   }
 
-  serialization->num_bytes = shared_buffer_->num_bytes();
+  serialization->num_bytes = shared_buffer_->GetNumBytes();
   serialization->platform_handle_index = platform_handles->size();
   platform_handles->push_back(platform_handle.release());
   *actual_size = sizeof(SerializedSharedBufferDispatcher);

mojo/system/shared_buffer_dispatcher.h

@@ -6,8 +6,8 @@
 #define MOJO_SYSTEM_SHARED_BUFFER_DISPATCHER_H_
 
 #include "base/macros.h"
+#include "mojo/embedder/platform_shared_buffer.h"
 #include "mojo/system/memory.h"
-#include "mojo/system/raw_shared_buffer.h"
 #include "mojo/system/simple_dispatcher.h"
 #include "mojo/system/system_impl_export.h"
 
@@ -53,7 +53,7 @@ class MOJO_SYSTEM_IMPL_EXPORT SharedBufferDispatcher : public SimpleDispatcher {
 
  private:
   explicit SharedBufferDispatcher(
-      scoped_refptr<RawSharedBuffer> shared_buffer_);
+      scoped_refptr<embedder::PlatformSharedBuffer> shared_buffer_);
   virtual ~SharedBufferDispatcher();
 
   // Validates and/or sets default options for
@@ -76,7 +76,7 @@ class MOJO_SYSTEM_IMPL_EXPORT SharedBufferDispatcher : public SimpleDispatcher {
       uint64_t offset,
       uint64_t num_bytes,
       MojoMapBufferFlags flags,
-      scoped_ptr<RawSharedBufferMapping>* mapping) OVERRIDE;
+      scoped_ptr<embedder::PlatformSharedBufferMapping>* mapping) OVERRIDE;
   virtual void StartSerializeImplNoLock(Channel* channel,
                                         size_t* max_size,
                                         size_t* max_platform_handles) OVERRIDE;
@@ -86,7 +86,7 @@ class MOJO_SYSTEM_IMPL_EXPORT SharedBufferDispatcher : public SimpleDispatcher {
       size_t* actual_size,
       embedder::PlatformHandleVector* platform_handles) OVERRIDE;
 
-  scoped_refptr<RawSharedBuffer> shared_buffer_;
+  scoped_refptr<embedder::PlatformSharedBuffer> shared_buffer_;
 
   DISALLOW_COPY_AND_ASSIGN(SharedBufferDispatcher);
 };

mojo/system/shared_buffer_dispatcher_unittest.cc

@@ -8,8 +8,8 @@
 
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
+#include "mojo/embedder/platform_shared_buffer.h"
 #include "mojo/system/dispatcher.h"
-#include "mojo/system/raw_shared_buffer.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace mojo {
@@ -109,31 +109,31 @@ TEST(SharedBufferDispatcherTest, CreateAndMapBuffer) {
   EXPECT_EQ(Dispatcher::kTypeSharedBuffer, dispatcher->GetType());
 
   // Make a couple of mappings.
-  scoped_ptr<RawSharedBufferMapping> mapping1;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping1;
   EXPECT_EQ(
       MOJO_RESULT_OK,
       dispatcher->MapBuffer(0, 100, MOJO_MAP_BUFFER_FLAG_NONE, &mapping1));
   ASSERT_TRUE(mapping1);
-  ASSERT_TRUE(mapping1->base());
-  EXPECT_EQ(100u, mapping1->length());
+  ASSERT_TRUE(mapping1->GetBase());
+  EXPECT_EQ(100u, mapping1->GetLength());
   // Write something.
-  static_cast<char*>(mapping1->base())[50] = 'x';
+  static_cast<char*>(mapping1->GetBase())[50] = 'x';
 
-  scoped_ptr<RawSharedBufferMapping> mapping2;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping2;
   EXPECT_EQ(
       MOJO_RESULT_OK,
       dispatcher->MapBuffer(50, 50, MOJO_MAP_BUFFER_FLAG_NONE, &mapping2));
   ASSERT_TRUE(mapping2);
-  ASSERT_TRUE(mapping2->base());
-  EXPECT_EQ(50u, mapping2->length());
-  EXPECT_EQ('x', static_cast<char*>(mapping2->base())[0]);
+  ASSERT_TRUE(mapping2->GetBase());
+  EXPECT_EQ(50u, mapping2->GetLength());
+  EXPECT_EQ('x', static_cast<char*>(mapping2->GetBase())[0]);
 
   EXPECT_EQ(MOJO_RESULT_OK, dispatcher->Close());
 
   // Check that we can still read/write to mappings after the dispatcher has
   // gone away.
-  static_cast<char*>(mapping2->base())[1] = 'y';
-  EXPECT_EQ('y', static_cast<char*>(mapping1->base())[51]);
+  static_cast<char*>(mapping2->GetBase())[1] = 'y';
+  EXPECT_EQ('y', static_cast<char*>(mapping1->GetBase())[51]);
 }
 
 TEST(SharedBufferDispatcher, DuplicateBufferHandle) {
@@ -144,11 +144,11 @@ TEST(SharedBufferDispatcher, DuplicateBufferHandle) {
           SharedBufferDispatcher::kDefaultCreateOptions, 100, &dispatcher1));
 
   // Map and write something.
-  scoped_ptr<RawSharedBufferMapping> mapping;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping;
   EXPECT_EQ(
       MOJO_RESULT_OK,
       dispatcher1->MapBuffer(0, 100, MOJO_MAP_BUFFER_FLAG_NONE, &mapping));
-  static_cast<char*>(mapping->base())[0] = 'x';
+  static_cast<char*>(mapping->GetBase())[0] = 'x';
   mapping.reset();
 
   // Duplicate |dispatcher1| and then close it.
@@ -165,7 +165,7 @@ TEST(SharedBufferDispatcher, DuplicateBufferHandle) {
   EXPECT_EQ(
       MOJO_RESULT_OK,
       dispatcher2->MapBuffer(0, 100, MOJO_MAP_BUFFER_FLAG_NONE, &mapping));
-  EXPECT_EQ('x', static_cast<char*>(mapping->base())[0]);
+  EXPECT_EQ('x', static_cast<char*>(mapping->GetBase())[0]);
 
   EXPECT_EQ(MOJO_RESULT_OK, dispatcher2->Close());
 }
@@ -250,7 +250,7 @@ TEST(SharedBufferDispatcherTest, MapBufferInvalidArguments) {
       SharedBufferDispatcher::Create(
           SharedBufferDispatcher::kDefaultCreateOptions, 100, &dispatcher));
 
-  scoped_ptr<RawSharedBufferMapping> mapping;
+  scoped_ptr<embedder::PlatformSharedBufferMapping> mapping;
   EXPECT_EQ(MOJO_RESULT_INVALID_ARGUMENT,
             dispatcher->MapBuffer(0, 101, MOJO_MAP_BUFFER_FLAG_NONE, &mapping));
   EXPECT_FALSE(mapping);