Fix progress reporting for multibuffers to report progress for every byte we receive.

media/blink/multibuffer.h

Index: media/blink/multibuffer.h
diff --git a/media/blink/multibuffer.h b/media/blink/multibuffer.h
index 29359b337e1f201132509080cf509f048e28347c..23280c8849074a3666b19be09af33e3230605235 100644
--- a/media/blink/multibuffer.h
+++ b/media/blink/multibuffer.h
@@ -114,6 +114,11 @@ class MEDIA_BLINK_EXPORT MultiBuffer {
     // availble to read.
     virtual bool Available() const = 0;
 
+    // Returns how many bytes are available, note that Available() may still
+    // return false even if AvailableBytes() returns a value greater than
+    // zero if less than a full block is available.
+    virtual int64_t AvailableBytes() const = 0;
+
     // Returns the next block. Only valid if Available()
     // returns true. Last block might be of a smaller size
     // and after the last block we will get an end-of-stream
@@ -249,6 +254,11 @@ class MEDIA_BLINK_EXPORT MultiBuffer {
   // Increment max cache size by |size| (counted in blocks).
   void IncrementMaxSize(int32_t size);
 
+  // Returns how many bytes have been received by the data providers at position
+  // |block|, which have not yet been submitted to the multibuffer cache.
+  // The returned number should be less than the size of one block.
+  int64_t UncommittedBytesAt(const BlockId& block);
+
   // Caller takes ownership of 'provider', cache will
   // not call it anymore.
   std::unique_ptr<DataProvider> RemoveProvider(DataProvider* provider);