Introduce VideoDecoder::HasOutputFrameAvailable().

By default HasOutputFrameAvailable() will return true since typically VideoFrames can be dynamically allocated. Decoders that use a fixed pool of pre-allocated VideoFrames can override this method to return false when all VideoFrames are currently spoken for.

VideoRendererBase now uses the result to determine whether it should finish prerolling.

BUG=177730


Review URL: https://chromiumcodereview.appspot.com/12902004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@189247 0039d316-1c4b-4281-b951-d872f2087c98

2 files changed, 10 insertions, 0 deletions

diff --git a/media/base/video_decoder.cc b/media/base/video_decoder.cc
index 4c7c4b7..dd1ab7c 100644
--- a/media/base/video_decoder.cc
+++ b/media/base/video_decoder.cc
@@ -14,4 +14,8 @@ bool VideoDecoder::HasAlpha() const {
   return false;
 }
 
+bool VideoDecoder::HasOutputFrameAvailable() const {
+  return true;
+}
+
 }  // namespace media
diff --git a/media/base/video_decoder.h b/media/base/video_decoder.h
index 915a9b4..904a6fd 100644
--- a/media/base/video_decoder.h
+++ b/media/base/video_decoder.h
@@ -69,6 +69,12 @@ class MEDIA_EXPORT VideoDecoder
   // that return formats with an alpha channel.
   virtual bool HasAlpha() const;
 
+  // Returns true if the decoder currently has the ability to decode and return
+  // a VideoFrame. Most implementations can allocate a new VideoFrame and hence
+  // this will always return true. Override and return false for decoders that
+  // use a fixed set of VideoFrames for decoding.
+  virtual bool HasOutputFrameAvailable() const;
+
  protected:
   friend class base::RefCountedThreadSafe<VideoDecoder>;
   virtual ~VideoDecoder();