Lazily prune the multibuffer block cache.

media/blink/url_index_unittest.cc

Index: media/blink/url_index_unittest.cc
diff --git a/media/blink/url_index_unittest.cc b/media/blink/url_index_unittest.cc
index 9a309cb8d39c904f772a28d60a0463174ffd0cd9..b8b23bfdb4ebac914fd0ef13d1d0f65ccd73f7a9 100644
--- a/media/blink/url_index_unittest.cc
+++ b/media/blink/url_index_unittest.cc
@@ -8,6 +8,7 @@
 #include <string>
 
 #include "base/logging.h"
+#include "base/message_loop/message_loop.h"
 #include "base/strings/stringprintf.h"
 #include "media/blink/url_index.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -26,6 +27,8 @@ class UrlIndexTest : public testing::Test {
     return ret;
   }
 
+  // TODO(hubbe): Make UrlIndex take a task_runner_
+  base::MessageLoop message_loop_;
   UrlIndex url_index_;
 };