Lazily prune the multibuffer block cache.

media/blink/multibuffer_data_source_unittest.cc

Index: media/blink/multibuffer_data_source_unittest.cc
diff --git a/media/blink/multibuffer_data_source_unittest.cc b/media/blink/multibuffer_data_source_unittest.cc
index d3e74474606386f67f3728bdc65e8f8e0cb6d0f2..816362a17ac42775d2c64285b929d6f7fec1f081 100644
--- a/media/blink/multibuffer_data_source_unittest.cc
+++ b/media/blink/multibuffer_data_source_unittest.cc
@@ -456,6 +456,7 @@ class MultibufferDataSourceTest : public testing::Test {
   WebView* view_;
   WebLocalFrame* frame_;
   MultibufferDataSource::Preload preload_;
+  base::MessageLoop message_loop_;
   linked_ptr<TestUrlIndex> url_index_;
 
   scoped_ptr<MockMultibufferDataSource> data_source_;
@@ -463,7 +464,6 @@ class MultibufferDataSourceTest : public testing::Test {
   scoped_ptr<TestResponseGenerator> response_generator_;
 
   StrictMock<MockBufferedDataSourceHost> host_;
-  base::MessageLoop message_loop_;
 
   // Used for calling MultibufferDataSource::Read().
   uint8_t buffer_[kDataSize * 2];