Fix a timing bug in multibuffer.

media/blink/multibuffer_data_source.cc

Index: media/blink/multibuffer_data_source.cc
diff --git a/media/blink/multibuffer_data_source.cc b/media/blink/multibuffer_data_source.cc
index a343fee303aef91f428fcad47dcf86f04ba6b61a..1390c69c36e78319d6f4063678258090b72bc099 100644
--- a/media/blink/multibuffer_data_source.cc
+++ b/media/blink/multibuffer_data_source.cc
@@ -416,7 +416,7 @@ void MultibufferDataSource::ReadTask() {
   } else {
     reader_->Wait(1, base::Bind(&MultibufferDataSource::ReadTask,
                                 weak_factory_.GetWeakPtr()));
-    UpdateLoadingState(false);
+    UpdateLoadingState_Locked(false);
   }
 }
 
@@ -507,7 +507,7 @@ void MultibufferDataSource::StartCallback() {
 
   // Even if data is cached, say that we're loading at this point for
   // compatibility.
-  UpdateLoadingState(true);
+  UpdateLoadingState_Locked(true);
 }
 
 void MultibufferDataSource::ProgressCallback(int64_t begin, int64_t end) {
@@ -517,25 +517,29 @@ void MultibufferDataSource::ProgressCallback(int64_t begin, int64_t end) {
   if (assume_fully_buffered())
     return;
 
+  base::AutoLock auto_lock(lock_);
+
   if (end > begin) {
     // TODO(scherkus): we shouldn't have to lock to signal host(), see
     // http://crbug.com/113712 for details.
-    base::AutoLock auto_lock(lock_);
     if (stop_signal_received_)
       return;
 
     host_->AddBufferedByteRange(begin, end);
   }
 
-  UpdateLoadingState(false);
+  UpdateLoadingState_Locked(false);
 }
 
-void MultibufferDataSource::UpdateLoadingState(bool force_loading) {
+void MultibufferDataSource::UpdateLoadingState_Locked(bool force_loading) {
   DVLOG(1) << __func__;
+  lock_.AssertAcquired();
   if (assume_fully_buffered())
     return;
   // Update loading state.
   bool is_loading = !!reader_ && reader_->IsLoading();
+  if (read_op_)
+    is_loading = true;
   if (force_loading || is_loading != loading_) {
     loading_ = is_loading || force_loading;