Move cc::RingBuffer to //base

It is used by content/browser/tracing/arc_tracing_agent_impl.{cc,h}, which,
logically, should not depend on chrome compositor.

Also, we want to move arc_tracing_agent_impl to //chrome/browser
(crrev/c/868575) but we do not want to add a dependency from //chrome/browser to
//cc/base ( https://cs.chromium.org/chromium/src/chrome/browser/DEPS?l=89).

TBR=oysteine@chromium.org

Bug: 808839
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_optional_gpu_tests_rel
Change-Id: I30adee8ee4f3c7e8c4f478f15e6841937b4be96c
Reviewed-on: https://chromium-review.googlesource.com/899858Reviewed-by: danakj <danakj@chromium.org>
Reviewed-by: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Commit-Queue: Ehsan Chiniforooshan <chiniforooshan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#534796}

cc/base/ring_buffer.h → base/containers/ring_buffer.h

@@ -2,16 +2,25 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CC_BASE_RING_BUFFER_H_
-#define CC_BASE_RING_BUFFER_H_
+#ifndef BASE_CONTAINERS_RING_BUFFER_H_
+#define BASE_CONTAINERS_RING_BUFFER_H_
 
 #include <stddef.h>
 
 #include "base/logging.h"
 #include "base/macros.h"
 
-namespace cc {
-
+namespace base {
+
+// base::RingBuffer uses a fixed-size array, unlike base::circular_deque and
+// std::deque, and so, one can access only the last |kSize| elements. Also, you
+// can add elements to the front and read/modify random elements, but cannot
+// remove elements from the back. Therefore, it does not have a |Size| method,
+// only |BufferSize|, which is a constant, and |CurrentIndex|, which is the
+// number of elements added so far.
+//
+// If the above is sufficient for your use case, base::RingBuffer should be more
+// efficient than base::circular_deque.
 template <typename T, size_t kSize>
 class RingBuffer {
  public:
@@ -105,6 +114,6 @@ class RingBuffer {
   DISALLOW_COPY_AND_ASSIGN(RingBuffer);
 };
 
-}  // namespace cc
+}  // namespace base
 
-#endif  // CC_BASE_RING_BUFFER_H_
+#endif  // BASE_CONTAINERS_RING_BUFFER_H_

cc/resources/memory_history.h

@@ -10,9 +10,9 @@
 
 #include <memory>
 
+#include "base/containers/ring_buffer.h"
 #include "base/macros.h"
 #include "base/time/time.h"
-#include "cc/base/ring_buffer.h"
 
 namespace cc {
 
@@ -36,7 +36,7 @@ class MemoryHistory {
 
   void SaveEntry(const Entry& entry);
 
-  typedef RingBuffer<Entry, 80> RingBufferType;
+  typedef base::RingBuffer<Entry, 80> RingBufferType;
   RingBufferType::Iterator Begin() const { return ring_buffer_.Begin(); }
   RingBufferType::Iterator End() const { return ring_buffer_.End(); }
 

cc/trees/frame_rate_counter.h

@@ -9,9 +9,9 @@
 
 #include <memory>
 
+#include "base/containers/ring_buffer.h"
 #include "base/macros.h"
 #include "base/time/time.h"
-#include "cc/base/ring_buffer.h"
 
 namespace cc {
 
@@ -40,7 +40,7 @@ class FrameRateCounter {
   void GetMinAndMaxFPS(double* min_fps, double* max_fps) const;
   double GetAverageFPS() const;
 
-  typedef RingBuffer<base::TimeTicks, 136> RingBufferType;
+  typedef base::RingBuffer<base::TimeTicks, 136> RingBufferType;
   RingBufferType::Iterator begin() const { return ring_buffer_.Begin(); }
   RingBufferType::Iterator end() const { return ring_buffer_.End(); }
 

content/browser/tracing/arc_tracing_agent_impl.h

@@ -9,12 +9,12 @@
 #include <string>
 
 #include "base/callback_forward.h"
+#include "base/containers/ring_buffer.h"
 #include "base/files/file_descriptor_watcher_posix.h"
 #include "base/files/scoped_file.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
-#include "cc/base/ring_buffer.h"
 #include "content/public/browser/arc_tracing_agent.h"
 #include "mojo/public/cpp/bindings/binding.h"
 #include "services/resource_coordinator/public/interfaces/tracing/tracing.mojom.h"
@@ -58,7 +58,7 @@ class ArcTracingAgentImpl : public ArcTracingAgent {
    private:
     base::ScopedFD read_fd_;
     std::unique_ptr<base::FileDescriptorWatcher::Controller> fd_watcher_;
-    cc::RingBuffer<std::string, kTraceEventBufferSize> ring_buffer_;
+    base::RingBuffer<std::string, kTraceEventBufferSize> ring_buffer_;
     // NOTE: Weak pointers must be invalidated before all other member variables
     // so it must be the last member.
     base::WeakPtrFactory<ArcTracingReader> weak_ptr_factory_;