components/arc: Add Flush() to the video_encode_accelerator interface.

BUG=755889
TEST=None

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I1780b6b54fa6de50594c995170724d888abc64ae
Reviewed-on: https://chromium-review.googlesource.com/720737
Commit-Queue: Owen Lin <owenlin@chromium.org>
Reviewed-by: Kuang-che Wu <kcwu@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#512450}

chrome/gpu/gpu_arc_video_encode_accelerator.cc

@@ -225,6 +225,15 @@ void GpuArcVideoEncodeAccelerator::RequestEncodingParametersChange(
   accelerator_->RequestEncodingParametersChange(bitrate, framerate);
 }
 
+void GpuArcVideoEncodeAccelerator::Flush(FlushCallback callback) {
+  DVLOGF(2);
+  if (!accelerator_) {
+    DLOG(ERROR) << "Accelerator is not initialized.";
+    return;
+  }
+  accelerator_->Flush(std::move(callback));
+}
+
 base::ScopedFD GpuArcVideoEncodeAccelerator::UnwrapFdFromMojoHandle(
     mojo::ScopedHandle handle) {
   DCHECK(client_);

chrome/gpu/gpu_arc_video_encode_accelerator.h

@@ -65,6 +65,7 @@ class GpuArcVideoEncodeAccelerator
                           UseBitstreamBufferCallback callback) override;
   void RequestEncodingParametersChange(uint32_t bitrate,
                                        uint32_t framerate) override;
+  void Flush(FlushCallback callback) override;
 
   // Unwraps a file descriptor from the given mojo::ScopedHandle.
   // If an error is encountered, it returns an invalid base::ScopedFD and

components/arc/common/video_encode_accelerator.mojom

@@ -72,7 +72,7 @@ struct VideoEncodeProfile {
 
 // Video encoder IPC interface.
 // Next MinVersion: 1
-// Next Method ID: 5
+// Next Method ID: 6
 interface VideoEncodeAccelerator {
 
   // The input buffer storage type.
@@ -162,6 +162,14 @@ interface VideoEncodeAccelerator {
   //  |framerate| is the requested new framerate, in frames per second.
   RequestEncodingParametersChange@4(uint32 bitrate,
                                     uint32 framerate);
+
+  // Flushes the encoder: all pending inputs will be encoded and all bitstreams
+  // handed back to the client. The client should not invoke Flush() or
+  // Encode() before the previous Flush() is finished.
+  // Callback:
+  //  Called with |true| if Flush() is complete; with |false| if Flush() is
+  //  canceled.
+  Flush@5() => (bool flush_done);
 };
 
 // Interface for clients that use VideoEncodeAccelerator. These callbacks will