Add offset support to BitstreamBuffer.

media/base/bitstream_buffer.h

Index: media/base/bitstream_buffer.h
diff --git a/media/base/bitstream_buffer.h b/media/base/bitstream_buffer.h
index 6ff1c059b98ff595a4a45bdac7302554c1d2c100..93947ba0d42337f30d4e6c2cce2f15f225f01fd9 100644
--- a/media/base/bitstream_buffer.h
+++ b/media/base/bitstream_buffer.h
@@ -23,6 +23,17 @@ class MEDIA_EXPORT BitstreamBuffer {
   BitstreamBuffer(int32 id,
                   base::SharedMemoryHandle handle,
                   size_t size,
+                  off_t offset);

[Pawel Osciak, 2015/12/31 02:05:54]

Please add documentation what offset and size are, as it's not obvious anymore.

[Owen Lin, 2016/01/04 08:54:18]

Done.

+
+  BitstreamBuffer(int32 id,
+                  base::SharedMemoryHandle handle,
+                  size_t size,
+                  base::TimeDelta presentation_timestamp);
+
+  BitstreamBuffer(int32 id,
+                  base::SharedMemoryHandle handle,
+                  size_t size,
+                  off_t offset,
                   base::TimeDelta presentation_timestamp);
 
   ~BitstreamBuffer();
@@ -31,8 +42,13 @@ class MEDIA_EXPORT BitstreamBuffer {
 
   int32 id() const { return id_; }
   base::SharedMemoryHandle handle() const { return handle_; }
+
+  // The number of bytes of the bitstream buffer.

[Pawel Osciak, 2015/12/31 02:05:54]

Please clarify if this is the size of the bitstream data inside the shared
memory buffer (data_size) only, or of the whole shared memory (i.e. offset +
data_size).

[Owen Lin, 2016/01/04 08:54:18]

Done.

   size_t size() const { return size_; }
 
+  // The offset of the bistream buffer to the shared memory.

[Pawel Osciak, 2015/12/31 02:05:54]

"Offset to the start of actual bitstream data in shared memory."

[Owen Lin, 2016/01/04 08:54:18]

Done.

+  off_t offset() const { return offset_; }
+
   // The timestamp is only valid if it's not equal to |media::kNoTimestamp()|.
   base::TimeDelta presentation_timestamp() const {
     return presentation_timestamp_;
@@ -48,6 +64,7 @@ class MEDIA_EXPORT BitstreamBuffer {
   int32 id_;
   base::SharedMemoryHandle handle_;
   size_t size_;
+  off_t offset_;
 
   // This is only set when necessary. For example, AndroidVideoDecodeAccelerator
   // needs the timestamp because the underlying decoder may require it to