[Mac] Remove FD-backed shared memory implementation.

There are no more users of this implementation, and the new shared
memory APIs do not support FD-backed shared memory on Mac.

Bug: 776564
Change-Id: I9307a6e46daa4329f0d04e6951b6e432a79c2c47
Reviewed-on: https://chromium-review.googlesource.com/c/1303873Reviewed-by: Alexandr Ilin <alexilin@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Robert Sesek <rsesek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603757}

base/memory/platform_shared_memory_region_mac.cc

@@ -57,7 +57,6 @@ PlatformSharedMemoryRegion::TakeFromSharedMemoryHandle(
     const SharedMemoryHandle& handle,
     Mode mode) {
   CHECK(mode == Mode::kReadOnly || mode == Mode::kUnsafe);
-  CHECK(handle.GetType() == SharedMemoryHandle::MACH);
   if (!handle.IsValid())
     return {};
 

base/memory/shared_memory.h

@@ -36,10 +36,7 @@ class FilePath;
 
 // Options for creating a shared memory object.
 struct BASE_EXPORT SharedMemoryCreateOptions {
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-  // The type of OS primitive that should back the SharedMemory object.
-  SharedMemoryHandle::Type type = SharedMemoryHandle::MACH;
-#elif !defined(OS_FUCHSIA)
+#if !defined(OS_FUCHSIA)
   // DEPRECATED (crbug.com/345734):
   // If NULL, the object is anonymous.  This pointer is owned by the caller
   // and must live through the call to Create().
@@ -51,7 +48,7 @@ struct BASE_EXPORT SharedMemoryCreateOptions {
   // shared memory must not exist.  This flag is meaningless unless
   // name_deprecated is non-NULL.
   bool open_existing_deprecated = false;
-#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
+#endif
 
   // Size of the shared memory object to be created.
   // When opening an existing object, this has no effect.
@@ -106,7 +103,7 @@ class BASE_EXPORT SharedMemory {
   // primitive.
   static SharedMemoryHandle DuplicateHandle(const SharedMemoryHandle& handle);
 
-#if defined(OS_POSIX)
+#if defined(OS_POSIX) && !(defined(OS_MACOSX) && !defined(OS_IOS))
   // This method requires that the SharedMemoryHandle is backed by a POSIX fd.
   static int GetFdFromSharedMemoryHandle(const SharedMemoryHandle& handle);
 #endif
@@ -231,12 +228,6 @@ class BASE_EXPORT SharedMemory {
   SharedMemoryHandle readonly_shm_;
 #endif
 
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-  // The mechanism by which the memory is mapped. Only valid if |memory_| is not
-  // |nullptr|.
-  SharedMemoryHandle::Type mapped_memory_mechanism_ = SharedMemoryHandle::MACH;
-#endif
-
   // The OS primitive that backs the shared memory region.
   SharedMemoryHandle shm_;
 

base/memory/shared_memory_handle.h

@@ -16,7 +16,6 @@
 #elif defined(OS_MACOSX) && !defined(OS_IOS)
 #include <mach/mach.h>
 #include "base/base_export.h"
-#include "base/file_descriptor_posix.h"
 #include "base/macros.h"
 #include "base/process/process_handle.h"
 #elif defined(OS_POSIX)
@@ -101,13 +100,6 @@ class BASE_EXPORT SharedMemoryHandle {
                      const base::UnguessableToken& guid);
   zx_handle_t GetHandle() const;
 #elif defined(OS_MACOSX) && !defined(OS_IOS)
-  enum Type {
-    // The SharedMemoryHandle is backed by a POSIX fd.
-    POSIX,
-    // The SharedMemoryHandle is backed by the Mach primitive "memory object".
-    MACH,
-  };
-
   // Makes a Mach-based SharedMemoryHandle of the given size. On error,
   // subsequent calls to IsValid() return false.
   // Passing the wrong |size| has no immediate consequence, but may cause errors
@@ -122,8 +114,6 @@ class BASE_EXPORT SharedMemoryHandle {
                      mach_vm_size_t size,
                      const base::UnguessableToken& guid);
 
-  Type GetType() const { return type_; }
-
   // Exposed so that the SharedMemoryHandle can be transported between
   // processes.
   mach_port_t GetMemoryObject() const;
@@ -165,7 +155,7 @@ class BASE_EXPORT SharedMemoryHandle {
   bool SetRegionReadOnly() const;
 #endif
 
-#if defined(OS_POSIX)
+#if defined(OS_POSIX) && !(defined(OS_MACOSX) && !defined(OS_IOS))
   // Constructs a SharedMemoryHandle backed by a FileDescriptor. The newly
   // created instance has the same ownership semantics as base::FileDescriptor.
   // This typically means that the SharedMemoryHandle takes ownership of the
@@ -203,14 +193,6 @@ class BASE_EXPORT SharedMemoryHandle {
   friend bool CheckReadOnlySharedMemoryHandleForTesting(
       SharedMemoryHandle handle);
 
-  Type type_ = MACH;
-
-  // Each instance of a SharedMemoryHandle is backed either by a POSIX fd or a
-  // mach port. |type_| determines the backing member.
-  union {
-    FileDescriptor file_descriptor_;
-
-    struct {
   mach_port_t memory_object_ = MACH_PORT_NULL;
 
   // Whether passing this object as a parameter to an IPC message passes
@@ -218,8 +200,6 @@ class BASE_EXPORT SharedMemoryHandle {
   // the behavior of the |auto_close| parameter of FileDescriptor.
   // Defaults to |false|.
   bool ownership_passes_to_ipc_ = false;
-    };
-  };
 #elif defined(OS_ANDROID)
   friend class SharedMemory;
 

base/memory/shared_memory_handle_mac.cc

@@ -6,30 +6,17 @@
 
 #include <mach/mach_vm.h>
 #include <stddef.h>
-#include <sys/mman.h>
-#include <unistd.h>
 
 #include "base/mac/mac_util.h"
 #include "base/mac/mach_logging.h"
-#include "base/posix/eintr_wrapper.h"
 #include "base/unguessable_token.h"
 
 namespace base {
 
 SharedMemoryHandle::SharedMemoryHandle() {}
 
-SharedMemoryHandle::SharedMemoryHandle(
-    const base::FileDescriptor& file_descriptor,
-    size_t size,
-    const base::UnguessableToken& guid)
-    : type_(POSIX),
-      file_descriptor_(file_descriptor),
-      guid_(guid),
-      size_(size) {}
-
 SharedMemoryHandle::SharedMemoryHandle(mach_vm_size_t size,
                                        const base::UnguessableToken& guid) {
-  type_ = MACH;
   mach_port_t named_right;
   kern_return_t kr = mach_make_memory_entry_64(
       mach_task_self(),
@@ -52,23 +39,12 @@ SharedMemoryHandle::SharedMemoryHandle(mach_vm_size_t size,
 SharedMemoryHandle::SharedMemoryHandle(mach_port_t memory_object,
                                        mach_vm_size_t size,
                                        const base::UnguessableToken& guid)
-    : type_(MACH),
-      memory_object_(memory_object),
+    : memory_object_(memory_object),
       ownership_passes_to_ipc_(false),
       guid_(guid),
       size_(size) {}
 
 SharedMemoryHandle SharedMemoryHandle::Duplicate() const {
-  switch (type_) {
-    case POSIX: {
-      if (!IsValid())
-        return SharedMemoryHandle();
-      int duped_fd = HANDLE_EINTR(dup(file_descriptor_.fd));
-      if (duped_fd < 0)
-        return SharedMemoryHandle();
-      return SharedMemoryHandle(FileDescriptor(duped_fd, true), size_, guid_);
-    }
-    case MACH: {
   if (!IsValid())
     return SharedMemoryHandle();
 
@@ -79,21 +55,13 @@ SharedMemoryHandle SharedMemoryHandle::Duplicate() const {
   SharedMemoryHandle handle(*this);
   handle.SetOwnershipPassesToIPC(true);
   return handle;
-    }
-  }
 }
 
 bool SharedMemoryHandle::IsValid() const {
-  switch (type_) {
-    case POSIX:
-      return file_descriptor_.fd >= 0;
-    case MACH:
   return memory_object_ != MACH_PORT_NULL;
-  }
 }
 
 mach_port_t SharedMemoryHandle::GetMemoryObject() const {
-  DCHECK_EQ(type_, MACH);
   return memory_object_;
 }
 
@@ -102,52 +70,32 @@ bool SharedMemoryHandle::MapAt(off_t offset,
                                void** memory,
                                bool read_only) {
   DCHECK(IsValid());
-  switch (type_) {
-    case SharedMemoryHandle::POSIX:
-      *memory = mmap(nullptr, bytes, PROT_READ | (read_only ? 0 : PROT_WRITE),
-                     MAP_SHARED, file_descriptor_.fd, offset);
-      return *memory != MAP_FAILED;
-    case SharedMemoryHandle::MACH:
   kern_return_t kr = mach_vm_map(
       mach_task_self(),
       reinterpret_cast<mach_vm_address_t*>(memory),  // Output parameter
       bytes,
       0,  // Alignment mask
-          VM_FLAGS_ANYWHERE,
-          memory_object_,
-          offset,
+      VM_FLAGS_ANYWHERE, memory_object_, offset,
       FALSE,                                           // Copy
       VM_PROT_READ | (read_only ? 0 : VM_PROT_WRITE),  // Current protection
       VM_PROT_WRITE | VM_PROT_READ | VM_PROT_IS_MASK,  // Maximum protection
       VM_INHERIT_NONE);
   return kr == KERN_SUCCESS;
-  }
 }
 
 void SharedMemoryHandle::Close() const {
   if (!IsValid())
     return;
 
-  switch (type_) {
-    case POSIX:
-      if (IGNORE_EINTR(close(file_descriptor_.fd)) < 0)
-        DPLOG(ERROR) << "Error closing fd";
-      break;
-    case MACH:
   kern_return_t kr = mach_port_deallocate(mach_task_self(), memory_object_);
-      if (kr != KERN_SUCCESS)
-        MACH_DLOG(ERROR, kr) << "Error deallocating mach port";
-      break;
-  }
+  MACH_DLOG_IF(ERROR, kr != KERN_SUCCESS, kr) << "Error deallocating mach port";
 }
 
 void SharedMemoryHandle::SetOwnershipPassesToIPC(bool ownership_passes) {
-  DCHECK_EQ(type_, MACH);
   ownership_passes_to_ipc_ = ownership_passes;
 }
 
 bool SharedMemoryHandle::OwnershipPassesToIPC() const {
-  DCHECK_EQ(type_, MACH);
   return ownership_passes_to_ipc_;
 }
 

base/memory/shared_memory_mac.cc

@@ -11,8 +11,6 @@
 #include <sys/stat.h>
 #include <unistd.h>
 
-#include "base/files/file_util.h"
-#include "base/files/scoped_file.h"
 #include "base/logging.h"
 #include "base/mac/foundation_util.h"
 #include "base/mac/mac_util.h"
@@ -21,12 +19,10 @@
 #include "base/memory/shared_memory_tracker.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram_macros.h"
-#include "base/posix/eintr_wrapper.h"
 #include "base/posix/safe_strerror.h"
 #include "base/process/process_metrics.h"
 #include "base/scoped_generic.h"
 #include "base/strings/utf_string_conversions.h"
-#include "base/threading/thread_restrictions.h"
 #include "base/unguessable_token.h"
 #include "build/build_config.h"
 
@@ -85,9 +81,7 @@ bool MakeMachSharedMemoryHandleReadOnly(SharedMemoryHandle* new_handle,
 SharedMemory::SharedMemory() {}
 
 SharedMemory::SharedMemory(const SharedMemoryHandle& handle, bool read_only)
-    : mapped_memory_mechanism_(SharedMemoryHandle::POSIX),
-      shm_(handle),
-      read_only_(read_only) {}
+    : shm_(handle), read_only_(read_only) {}
 
 SharedMemory::~SharedMemory() {
   Unmap();
@@ -115,12 +109,6 @@ SharedMemoryHandle SharedMemory::DuplicateHandle(
   return handle.Duplicate();
 }
 
-// static
-int SharedMemory::GetFdFromSharedMemoryHandle(
-    const SharedMemoryHandle& handle) {
-  return handle.file_descriptor_.fd;
-}
-
 bool SharedMemory::CreateAndMapAnonymous(size_t size) {
   return CreateAnonymous(size) && Map(size);
 }
@@ -135,48 +123,9 @@ bool SharedMemory::Create(const SharedMemoryCreateOptions& options) {
   if (options.size > static_cast<size_t>(std::numeric_limits<int>::max()))
     return false;
 
-  if (options.type == SharedMemoryHandle::MACH) {
   shm_ = SharedMemoryHandle(options.size, UnguessableToken::Create());
   requested_size_ = options.size;
   return shm_.IsValid();
-  }
-
-  // This function theoretically can block on the disk. Both profiling of real
-  // users and local instrumentation shows that this is a real problem.
-  // https://code.google.com/p/chromium/issues/detail?id=466437
-  ThreadRestrictions::ScopedAllowIO allow_io;
-
-  ScopedFD fd;
-  ScopedFD readonly_fd;
-
-  FilePath path;
-  bool result = CreateAnonymousSharedMemory(options, &fd, &readonly_fd, &path);
-  if (!result)
-    return false;
-  // Should be guaranteed by CreateAnonymousSharedMemory().
-  DCHECK(fd.is_valid());
-
-  // Get current size.
-  struct stat stat;
-  if (fstat(fd.get(), &stat) != 0)
-    return false;
-  const size_t current_size = stat.st_size;
-  if (current_size != options.size) {
-    if (HANDLE_EINTR(ftruncate(fd.get(), options.size)) != 0)
-      return false;
-  }
-  requested_size_ = options.size;
-
-  int mapped_file = -1;
-  int readonly_mapped_file = -1;
-  result = PrepareMapFile(std::move(fd), std::move(readonly_fd), &mapped_file,
-                          &readonly_mapped_file);
-  shm_ = SharedMemoryHandle(FileDescriptor(mapped_file, false), options.size,
-                            UnguessableToken::Create());
-  readonly_shm_ =
-      SharedMemoryHandle(FileDescriptor(readonly_mapped_file, false),
-                         options.size, shm_.GetGUID());
-  return result;
 }
 
 bool SharedMemory::MapAt(off_t offset, size_t bytes) {
@@ -192,7 +141,6 @@ bool SharedMemory::MapAt(off_t offset, size_t bytes) {
     mapped_size_ = bytes;
     DCHECK_EQ(0U, reinterpret_cast<uintptr_t>(memory_) &
                       (SharedMemory::MAP_MINIMUM_ALIGNMENT - 1));
-    mapped_memory_mechanism_ = shm_.type_;
     mapped_id_ = shm_.GetGUID();
     SharedMemoryTracker::GetInstance()->IncrementMemoryUsage(*this);
   } else {
@@ -207,16 +155,9 @@ bool SharedMemory::Unmap() {
     return false;
 
   SharedMemoryTracker::GetInstance()->DecrementMemoryUsage(*this);
-  switch (mapped_memory_mechanism_) {
-    case SharedMemoryHandle::POSIX:
-      munmap(memory_, mapped_size_);
-      break;
-    case SharedMemoryHandle::MACH:
       mach_vm_deallocate(mach_task_self(),
                          reinterpret_cast<mach_vm_address_t>(memory_),
                          mapped_size_);
-      break;
-  }
   memory_ = nullptr;
   mapped_size_ = 0;
   mapped_id_ = UnguessableToken();
@@ -237,22 +178,9 @@ SharedMemoryHandle SharedMemory::TakeHandle() {
 void SharedMemory::Close() {
   shm_.Close();
   shm_ = SharedMemoryHandle();
-  if (shm_.type_ == SharedMemoryHandle::POSIX) {
-    if (readonly_shm_.IsValid()) {
-      readonly_shm_.Close();
-      readonly_shm_ = SharedMemoryHandle();
-    }
-  }
 }
 
 SharedMemoryHandle SharedMemory::GetReadOnlyHandle() const {
-  if (shm_.type_ == SharedMemoryHandle::POSIX) {
-    // We could imagine re-opening the file from /dev/fd, but that can't make it
-    // readonly on Mac: https://codereview.chromium.org/27265002/#msg10.
-    CHECK(readonly_shm_.IsValid());
-    return readonly_shm_.Duplicate();
-  }
-
   DCHECK(shm_.IsValid());
   SharedMemoryHandle new_handle;
   bool success = MakeMachSharedMemoryHandleReadOnly(&new_handle, shm_, memory_);

base/memory/shared_memory_unittest.cc

@@ -359,6 +359,8 @@ TEST_P(SharedMemoryTest, AnonymousPrivate) {
   }
 }
 
+#if !(defined(OS_MACOSX) && !defined(OS_IOS))
+// The Mach functionality is tested in shared_memory_mac_unittest.cc.
 TEST_P(SharedMemoryTest, GetReadOnlyHandle) {
   StringPiece contents = "Hello World";
 
@@ -366,10 +368,6 @@ TEST_P(SharedMemoryTest, GetReadOnlyHandle) {
   SharedMemoryCreateOptions options;
   options.size = contents.size();
   options.share_read_only = true;
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-  // The Mach functionality is tested in shared_memory_mac_unittest.cc.
-  options.type = SharedMemoryHandle::POSIX;
-#endif
   ASSERT_TRUE(writable_shmem.Create(options));
   ASSERT_TRUE(writable_shmem.Map(options.size));
   memcpy(writable_shmem.memory(), contents.data(), contents.size());
@@ -467,6 +465,7 @@ TEST_P(SharedMemoryTest, GetReadOnlyHandle) {
 #error Unexpected platform; write a test that tries to make 'handle' writable.
 #endif  // defined(OS_POSIX) || defined(OS_WIN)
 }
+#endif  // defined(OS_MACOSX) && !defined(OS_IOS)
 
 TEST_P(SharedMemoryTest, ShareToSelf) {
   StringPiece contents = "Hello World";
@@ -584,7 +583,8 @@ TEST_P(SharedMemoryTest, MapTwice) {
 
 #if defined(OS_POSIX)
 // This test is not applicable for iOS (crbug.com/399384).
-#if !defined(OS_IOS)
+// The Mach functionality is tested in shared_memory_mac_unittest.cc.
+#if !defined(OS_MACOSX) && !defined(OS_IOS)
 // Create a shared memory object, mmap it, and mprotect it to PROT_EXEC.
 TEST_P(SharedMemoryTest, AnonymousExecutable) {
 #if defined(OS_LINUX)
@@ -602,10 +602,6 @@ TEST_P(SharedMemoryTest, AnonymousExecutable) {
   SharedMemoryCreateOptions options;
   options.size = kTestSize;
   options.executable = true;
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-  // The Mach functionality is tested in shared_memory_mac_unittest.cc.
-  options.type = SharedMemoryHandle::POSIX;
-#endif
 
   EXPECT_TRUE(shared_memory.Create(options));
   EXPECT_TRUE(shared_memory.Map(shared_memory.requested_size()));
@@ -613,7 +609,7 @@ TEST_P(SharedMemoryTest, AnonymousExecutable) {
   EXPECT_EQ(0, mprotect(shared_memory.memory(), shared_memory.requested_size(),
                         PROT_READ | PROT_EXEC));
 }
-#endif  // !defined(OS_IOS)
+#endif  // !defined(OS_MACOSX) && !defined(OS_IOS)
 
 #if defined(OS_ANDROID)
 // This test is restricted to Android since there is no way on other platforms
@@ -658,16 +654,14 @@ class ScopedUmaskSetter {
 };
 
 // Create a shared memory object, check its permissions.
+#if !(defined(OS_MACOSX) && !defined(OS_IOS))
+// The Mach functionality is tested in shared_memory_mac_unittest.cc.
 TEST_P(SharedMemoryTest, FilePermissionsAnonymous) {
   const uint32_t kTestSize = 1 << 8;
 
   SharedMemory shared_memory;
   SharedMemoryCreateOptions options;
   options.size = kTestSize;
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-  // The Mach functionality is tested in shared_memory_mac_unittest.cc.
-  options.type = SharedMemoryHandle::POSIX;
-#endif
   // Set a file mode creation mask that gives all permissions.
   ScopedUmaskSetter permissive_mask(S_IWGRP | S_IWOTH);
 
@@ -682,18 +676,17 @@ TEST_P(SharedMemoryTest, FilePermissionsAnonymous) {
   EXPECT_FALSE(shm_stat.st_mode & S_IRWXO);
   EXPECT_FALSE(shm_stat.st_mode & S_IRWXG);
 }
+#endif  // !(defined(OS_MACOSX) && !defined(OS_IOS)
 
 // Create a shared memory object, check its permissions.
+#if !(defined(OS_MACOSX) && !defined(OS_IOS))
+// The Mach functionality is tested in shared_memory_mac_unittest.cc.
 TEST_P(SharedMemoryTest, FilePermissionsNamed) {
   const uint32_t kTestSize = 1 << 8;
 
   SharedMemory shared_memory;
   SharedMemoryCreateOptions options;
   options.size = kTestSize;
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-  // The Mach functionality is tested in shared_memory_mac_unittest.cc.
-  options.type = SharedMemoryHandle::POSIX;
-#endif
 
   // Set a file mode creation mask that gives all permissions.
   ScopedUmaskSetter permissive_mask(S_IWGRP | S_IWOTH);
@@ -708,6 +701,7 @@ TEST_P(SharedMemoryTest, FilePermissionsNamed) {
   EXPECT_FALSE(shm_stat.st_mode & S_IRWXO);
   EXPECT_FALSE(shm_stat.st_mode & S_IRWXG);
 }
+#endif  // !(defined(OS_MACOSX) && !defined(OS_IOS)
 #endif  // !defined(OS_ANDROID) && !defined(OS_FUCHSIA)
 
 #endif  // defined(OS_POSIX)
@@ -854,15 +848,13 @@ MULTIPROCESS_TEST_MAIN(SharedMemoryTestMain) {
 #endif  // !defined(OS_IOS) && !defined(OS_ANDROID) && !defined(OS_MACOSX) &&
         // !defined(OS_FUCHSIA)
 
+#if !(defined(OS_MACOSX) && !defined(OS_IOS))
+// The Mach functionality is tested in shared_memory_mac_unittest.cc.
 TEST_P(SharedMemoryTest, MappedId) {
   const uint32_t kDataSize = 1024;
   SharedMemory memory;
   SharedMemoryCreateOptions options;
   options.size = kDataSize;
-#if defined(OS_MACOSX) && !defined(OS_IOS)
-  // The Mach functionality is tested in shared_memory_mac_unittest.cc.
-  options.type = SharedMemoryHandle::POSIX;
-#endif
 
   EXPECT_TRUE(memory.Create(options));
   base::UnguessableToken id = memory.handle().GetGUID();
@@ -878,6 +870,7 @@ TEST_P(SharedMemoryTest, MappedId) {
   memory.Unmap();
   EXPECT_TRUE(memory.mapped_id().is_empty());
 }
+#endif  // !(defined(OS_MACOSX) && !defined(OS_IOS)
 
 INSTANTIATE_TEST_CASE_P(Default,
                         SharedMemoryTest,

base/test/test_shared_memory_util.cc

@@ -41,7 +41,7 @@ static const size_t kDataSize = 1024;
 // Common routine used with Posix file descriptors. Check that shared memory
 // file descriptor |fd| does not allow writable mappings. Return true on
 // success, false otherwise.
-#if defined(OS_POSIX)
+#if defined(OS_POSIX) && !(defined(OS_MACOSX) && !defined(OS_IOS))
 static bool CheckReadOnlySharedMemoryFdPosix(int fd) {
 // Note that the error on Android is EPERM, unlike other platforms where
 // it will be EACCES.
@@ -66,7 +66,7 @@ static bool CheckReadOnlySharedMemoryFdPosix(int fd) {
   }
   return true;
 }
-#endif  // OS_POSIX
+#endif  // OS_POSIX && !(defined(OS_MACOSX) && !defined(OS_IOS))
 
 #if defined(OS_FUCHSIA)
 // Fuchsia specific implementation.
@@ -118,10 +118,6 @@ bool CheckReadOnlySharedMemoryWindowsHandle(HANDLE handle) {
 
 bool CheckReadOnlySharedMemoryHandleForTesting(SharedMemoryHandle handle) {
 #if defined(OS_MACOSX) && !defined(OS_IOS)
-  // For OSX, the code has to deal with both POSIX and MACH handles.
-  if (handle.type_ == SharedMemoryHandle::POSIX)
-    return CheckReadOnlySharedMemoryFdPosix(handle.file_descriptor_.fd);
-  else
   return CheckReadOnlySharedMemoryMachPort(handle.memory_object_);
 #elif defined(OS_FUCHSIA)
   return CheckReadOnlySharedMemoryFuchsiaHandle(