Motown: Ffmpeg video decoder

services/media/framework_ffmpeg/ffmpeg_decoder_base.h

Index: services/media/framework_ffmpeg/ffmpeg_decoder_base.h
diff --git a/services/media/framework_ffmpeg/ffmpeg_decoder_base.h b/services/media/framework_ffmpeg/ffmpeg_decoder_base.h
index 3cb4afe3bec466bd301d3b6555443417e3014fde..63dd2ed3dd3f271e4975fcb7d34c42b337c65ede 100644
--- a/services/media/framework_ffmpeg/ffmpeg_decoder_base.h
+++ b/services/media/framework_ffmpeg/ffmpeg_decoder_base.h
@@ -35,6 +35,55 @@ class FfmpegDecoderBase : public Decoder {
                        PacketPtr* output) override;
 
  protected:
+  // Used to control deallocation of buffers.
+  class AvBufferContext {
+   public:
+    AvBufferContext(size_t size, PayloadAllocator* allocator)
+        : size_(size), allocator_(allocator) {
+      DCHECK(allocator_);
+      if (size_ == 0) {
+        buffer_ = nullptr;
+      } else {
+        buffer_ =
+            static_cast<uint8_t*>(allocator_->AllocatePayloadBuffer(size_));
+      }
+    }
+
+    ~AvBufferContext() {
+      if (allocator_ == nullptr) {
+        // Previously released.
+        return;
+      }
+
+      if (size_ != 0) {
+        DCHECK(buffer_ != nullptr);
+        allocator_->ReleasePayloadBuffer(size_, buffer_);
+        return;
+      }
+
+      DCHECK(buffer_ == nullptr);
+    }
+
+    uint8_t* buffer() { return buffer_; }
+
+    size_t size() { return size_; }
+
+    // Releases ownership of the buffer.
+    uint8_t* Release() {
+      DCHECK(allocator_) << "AvBufferContext released twice";
+      uint8_t* result = buffer_;
+      buffer_ = nullptr;
+      size_ = 0;
+      allocator_ = nullptr;
+      return result;
+    }
+
+   private:
+    uint8_t* buffer_;
+    size_t size_;
+    PayloadAllocator* allocator_;
+  };
+
   // Decodes from av_packet into av_frame_ptr. The result indicates how many
   // bytes were consumed from av_packet_. *frame_decoded_out indicates whether
   // av_frame_ptr contains a complete frame.