Adding callback support to media filter Initialize() and Seek().

media/base/filters.h

Index: media/base/filters.h
diff --git a/media/base/filters.h b/media/base/filters.h
index b892961aaf5473729857d5f1544de22b000af730..84df0966534fe5d83796d6780d0c4c89d38e14e6 100644
--- a/media/base/filters.h
+++ b/media/base/filters.h
@@ -53,6 +53,8 @@ enum FilterType {
   FILTER_VIDEO_RENDERER
 };
 
+// Used for completing asynchronous methods.
+typedef Callback0::Type FilterCallback;
 
 class MediaFilter : public base::RefCountedThreadSafe<MediaFilter> {
  public:
@@ -94,9 +96,14 @@ class MediaFilter : public base::RefCountedThreadSafe<MediaFilter> {
   // method if they need to respond to this call.
   virtual void SetPlaybackRate(float playback_rate) {}
 
-  // The pipeline is seeking to the specified time.  Filters may implement
-  // this method if they need to respond to this call.
-  virtual void Seek(base::TimeDelta time) {}
+  // Carry out any actions required to seek to the given time, executing the
+  // callback upon completion.
+  virtual void Seek(base::TimeDelta time, FilterCallback* callback) {
+    scoped_ptr<FilterCallback> seek_callback(callback);
+    if (seek_callback.get()) {
+      seek_callback->Run();
+    }
+  }
 
  protected:
   // Only allow scoped_refptr<> to delete filters.
@@ -128,8 +135,9 @@ class DataSource : public MediaFilter {
 
   static const size_t kReadError = static_cast<size_t>(-1);
 
-  // Initializes this filter, returns true if successful, false otherwise.
-  virtual bool Initialize(const std::string& url) = 0;
+  // Initialize a DataSource for the given URL, executing the callback upon
+  // completion.
+  virtual void Initialize(const std::string& url, FilterCallback* callback) = 0;
 
   // Returns the MediaFormat for this filter.
   virtual const MediaFormat& media_format() = 0;
@@ -166,8 +174,10 @@ class Demuxer : public MediaFilter {
             mime_type == mime_type::kApplicationOctetStream);
   }
 
-  // Initializes this filter, returns true if successful, false otherwise.
-  virtual bool Initialize(DataSource* data_source) = 0;
+  // Initialize a Demuxer with the given DataSource, executing the callback upon
+  // completion.
+  virtual void Initialize(DataSource* data_source,
+                          FilterCallback* callback) = 0;
 
   // Returns the number of streams available
   virtual size_t GetNumberOfStreams() = 0;
@@ -223,8 +233,9 @@ class VideoDecoder : public MediaFilter {
     return mime_type::kMajorTypeVideo;
   }
 
-  // Initializes this filter, returns true if successful, false otherwise.
-  virtual bool Initialize(DemuxerStream* demuxer_stream) = 0;
+  // Initialize a VideoDecoder with the given DemuxerStream, executing the
+  // callback upon completion.
+  virtual void Initialize(DemuxerStream* stream, FilterCallback* callback) = 0;
 
   // Returns the MediaFormat for this filter.
   virtual const MediaFormat& media_format() = 0;
@@ -246,8 +257,9 @@ class AudioDecoder : public MediaFilter {
     return mime_type::kMajorTypeAudio;
   }
 
-  // Initializes this filter, returns true if successful, false otherwise.
-  virtual bool Initialize(DemuxerStream* demuxer_stream) = 0;
+  // Initialize a AudioDecoder with the given DemuxerStream, executing the
+  // callback upon completion.
+  virtual void Initialize(DemuxerStream* stream, FilterCallback* callback) = 0;
 
   // Returns the MediaFormat for this filter.
   virtual const MediaFormat& media_format() = 0;
@@ -269,8 +281,9 @@ class VideoRenderer : public MediaFilter {
     return mime_type::kMajorTypeVideo;
   }
 
-  // Initializes this filter, returns true if successful, false otherwise.
-  virtual bool Initialize(VideoDecoder* decoder) = 0;
+  // Initialize a VideoRenderer with the given VideoDecoder, executing the
+  // callback upon completion.
+  virtual void Initialize(VideoDecoder* decoder, FilterCallback* callback) = 0;
 };
 
 
@@ -284,8 +297,9 @@ class AudioRenderer : public MediaFilter {
     return mime_type::kMajorTypeAudio;
   }
 
-  // Initializes this filter, returns true if successful, false otherwise.
-  virtual bool Initialize(AudioDecoder* decoder) = 0;
+  // Initialize a AudioRenderer with the given AudioDecoder, executing the
+  // callback upon completion.
+  virtual void Initialize(AudioDecoder* decoder, FilterCallback* callback) = 0;
 
   // Sets the output volume.
   virtual void SetVolume(float volume) = 0;