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

media/blink/multibuffer_reader.cc

Index: media/blink/multibuffer_reader.cc
diff --git a/media/blink/multibuffer_reader.cc b/media/blink/multibuffer_reader.cc
index 1872110112e49c866cfc94a97e2228c0db8db96d..cd894d5b81c33a9ea0045326f56a649db147af15 100644
--- a/media/blink/multibuffer_reader.cc
+++ b/media/blink/multibuffer_reader.cc
@@ -178,13 +178,14 @@ void MultiBufferReader::NotifyAvailableRange(
     // there are no callbacks from us after we've been destroyed.
     base::MessageLoop::current()->PostTask(
         FROM_HERE,
-        base::Bind(&MultiBufferReader::Call, weak_factory_.GetWeakPtr(),
-                   base::Bind(progress_callback_,
-                              static_cast<int64_t>(range.begin)
-                                  << multibuffer_->block_size_shift(),
-                              static_cast<int64_t>(range.end)
-                                  << multibuffer_->block_size_shift())));
-    // We may be destroyed, do not touch |this|.
+        base::Bind(
+            &MultiBufferReader::Call, weak_factory_.GetWeakPtr(),
+            base::Bind(progress_callback_,
+                       static_cast<int64_t>(range.begin)
+                           << multibuffer_->block_size_shift(),
+                       (static_cast<int64_t>(range.end)
+                        << multibuffer_->block_size_shift()) +
+                           multibuffer_->UncommittedBytesAt(range.end))));
   }
 }