Use explicit flush for ArcVideoAccelerator.

chrome/gpu/arc_video_accelerator.h

Index: chrome/gpu/arc_video_accelerator.h
diff --git a/chrome/gpu/arc_video_accelerator.h b/chrome/gpu/arc_video_accelerator.h
index bb7fa622358e9f37b7a4309f4386f0be2f2f23c6..b9c2d1e7b4723844d3979eba99fe77850b6226fd 100644
--- a/chrome/gpu/arc_video_accelerator.h
+++ b/chrome/gpu/arc_video_accelerator.h
@@ -27,13 +27,9 @@ enum PortType {
   PORT_COUNT = 2,
 };
 
-enum BufferFlag {
-  BUFFER_FLAG_EOS = 1 << 0,
-};
-
 struct BufferMetadata {
   int64_t timestamp = 0;  // in microseconds
-  uint32_t flags = 0;     // Flags defined in BufferFlag.
+  uint32_t flags = 0;     // Not used.

[dcheng, 2016/05/07 06:18:11]

Why do we need to keep this unused field?

[Owen Lin, 2016/05/09 07:04:41]

Just get a feeling it will be used soon. Let's remove it and add back when we
really need it.

   uint32_t bytes_used = 0;
 };
 
@@ -101,6 +97,9 @@ class ArcVideoAccelerator {
 
     // Called as a completion notification for Reset().
     virtual void OnResetDone() = 0;
+
+    // Called as a completion notification for Flush().
+    virtual void OnFlushDone() = 0;
   };
 
   // Initializes the ArcVideoAccelerator with specific configuration. This
@@ -142,6 +141,10 @@ class ArcVideoAccelerator {
   // and there won't be more callbacks.
   virtual void Reset() = 0;
 
+  // Flushes the accelerator. After all the output buffers have been returned
+  // to client by OnBufferDone(), Client::OnFlushDone() will be called.

[Pawel Osciak, 2016/05/09 07:27:39]

I think this is after all frames pending decode and/or display have been
returned, but not specifically all output buffers (we won't get empty buffers
back)?

[Owen Lin, 2016/05/10 08:26:33]

Comments modified accordingly.

+  virtual void Flush() = 0;
+
   virtual ~ArcVideoAccelerator() {}
 };