Add GUARDED_BY annotations to //media/blink.

Adding the annotation makes it clear which fields are protected by
base::Lock, and enables compile-time analysis to verify this.

BUG=893739,887645
TEST=compiles

Change-Id: Ibf8ff9b73f218fcd3cfeb4387e7ad406418ef522
Reviewed-on: https://chromium-review.googlesource.com/c/1303405Reviewed-by: Dale Curtis <dalecurtis@chromium.org>
Commit-Queue: John Rummell <jrummell@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604802}

media/blink/video_frame_compositor.h

@@ -12,6 +12,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/single_thread_task_runner.h"
 #include "base/synchronization/lock.h"
+#include "base/thread_annotations.h"
 #include "base/time/tick_clock.h"
 #include "base/time/time.h"
 #include "base/timer/timer.h"
@@ -144,8 +145,6 @@ class MEDIA_BLINK_EXPORT VideoFrameCompositor : public VideoRendererSink,
     tick_clock_ = tick_clock;
   }
 
-  void clear_current_frame_for_testing() { current_frame_ = nullptr; }
-
   // Enables or disables background rendering. If |enabled|, |timeout| is the
   // amount of time to wait after the last Render() call before starting the
   // background rendering mode.  Note, this can not disable the background
@@ -218,13 +217,14 @@ class MEDIA_BLINK_EXPORT VideoFrameCompositor : public VideoRendererSink,
   OnNewProcessedFrameCB new_processed_frame_cb_;
   cc::UpdateSubmissionStateCB update_submission_state_callback_;
 
-  // Set on the compositor thread, but also read on the media thread.
+  // Set on the compositor thread, but also read on the media thread. Lock is
+  // not used when reading |current_frame_| on the compositor thread.
   base::Lock current_frame_lock_;
   scoped_refptr<VideoFrame> current_frame_;
 
   // These values are updated and read from the media and compositor threads.
   base::Lock callback_lock_;
-  VideoRendererSink::RenderCallback* callback_;
+  VideoRendererSink::RenderCallback* callback_ GUARDED_BY(callback_lock_);
 
   // AutoOpenCloseEvent for begin/end events.
   std::unique_ptr<base::trace_event::AutoOpenCloseEvent> auto_open_close_;

media/blink/webaudiosourceprovider_impl.cc

@@ -15,6 +15,7 @@
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/single_thread_task_runner.h"
+#include "base/thread_annotations.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "media/audio/null_audio_sink.h"
 #include "media/base/audio_timestamp_helper.h"
@@ -101,7 +102,7 @@ class WebAudioSourceProviderImpl::TeeFilter
   // acquire a lock to read |copy_audio_bus_callback_| when necessary.
   std::atomic<bool> copy_required_;
   base::Lock copy_lock_;
-  CopyAudioCB copy_audio_bus_callback_;
+  CopyAudioCB copy_audio_bus_callback_ GUARDED_BY(copy_lock_);
 
   DISALLOW_COPY_AND_ASSIGN(TeeFilter);
 };

media/blink/webaudiosourceprovider_impl.h

@@ -14,6 +14,7 @@
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "base/synchronization/lock.h"
+#include "base/thread_annotations.h"
 #include "media/base/audio_renderer_sink.h"
 #include "media/blink/media_blink_export.h"
 #include "third_party/blink/public/platform/web_audio_source_provider.h"
@@ -101,7 +102,7 @@ class MEDIA_BLINK_EXPORT WebAudioSourceProviderImpl
 
   // Where audio ends up unless overridden by |client_|.
   base::Lock sink_lock_;
-  scoped_refptr<SwitchableAudioRendererSink> sink_;
+  scoped_refptr<SwitchableAudioRendererSink> sink_ GUARDED_BY(sink_lock_);
   std::unique_ptr<AudioBus> bus_wrapper_;
 
   // An inner class acting as a T filter where actual data can be tapped.