Use ScopedTaskEnvironment instead of MessageLoop in content unit tests.

content/browser/appcache/mock_appcache_storage_unittest.cc

Index: content/browser/appcache/mock_appcache_storage_unittest.cc
diff --git a/content/browser/appcache/mock_appcache_storage_unittest.cc b/content/browser/appcache/mock_appcache_storage_unittest.cc
index bee5ff03252f4ec8c0d5bb2a618f6accef1b48d4..55fb914932b1cd1a94da23aa371f7540e9750c07 100644
--- a/content/browser/appcache/mock_appcache_storage_unittest.cc
+++ b/content/browser/appcache/mock_appcache_storage_unittest.cc
@@ -6,6 +6,7 @@
 #include <stdint.h>
 
 #include "base/run_loop.h"
+#include "base/test/scoped_task_environment.h"
 #include "content/browser/appcache/appcache.h"
 #include "content/browser/appcache/appcache_group.h"
 #include "content/browser/appcache/appcache_response.h"
@@ -82,7 +83,7 @@ class MockAppCacheStorageTest : public testing::Test {
   };
 
  private:
-  base::MessageLoop message_loop_;
+  base::test::ScopedTaskEnvironment scoped_task_environment_;
 };
 
 TEST_F(MockAppCacheStorageTest, LoadCache_Miss) {