Reduce usage of MessageLoopProxy in base/

base/observer_list_threadsafe.h

Index: base/observer_list_threadsafe.h
diff --git a/base/observer_list_threadsafe.h b/base/observer_list_threadsafe.h
index 70b4f11ffa60ca252f5a5d7b69ed047851ea41ca..f9702ba66cfbee2b1398d067a8e9ca9709b319b3 100644
--- a/base/observer_list_threadsafe.h
+++ b/base/observer_list_threadsafe.h
@@ -14,9 +14,10 @@
 #include "base/logging.h"
 #include "base/memory/ref_counted.h"
 #include "base/message_loop/message_loop.h"
-#include "base/message_loop/message_loop_proxy.h"
 #include "base/observer_list.h"
+#include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
+#include "base/thread_task_runner_handle.h"
 #include "base/threading/platform_thread.h"
 
 ///////////////////////////////////////////////////////////////////////////////
@@ -208,11 +209,9 @@ class ObserverListThreadSafe
 
   struct ObserverListContext {
     explicit ObserverListContext(NotificationType type)
-        : loop(base::MessageLoopProxy::current()),
-          list(type) {
-    }
+        : task_runner(base::ThreadTaskRunnerHandle::Get()), list(type) {}
 
-    scoped_refptr<base::MessageLoopProxy> loop;
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner;
     ObserverList<ObserverType> list;
 
     DISALLOW_COPY_AND_ASSIGN(ObserverListContext);
@@ -228,10 +227,13 @@ class ObserverListThreadSafe
     typename ObserversListMap::iterator it;
     for (it = observer_lists_.begin(); it != observer_lists_.end(); ++it) {
       ObserverListContext* context = (*it).second;
-      context->loop->PostTask(
+      context->task_runner->PostTask(
           FROM_HERE,
-          base::Bind(&ObserverListThreadSafe<ObserverType>::
-              template NotifyWrapper<Method, Params>, this, context, method));
+          base::Bind(&ObserverListThreadSafe<
+                         ObserverType>::template NotifyWrapper<Method, Params>,
+                     this,
+                     context,
+                     method));
     }
   }
 
@@ -249,7 +251,7 @@ class ObserverListThreadSafe
           observer_lists_.find(base::PlatformThread::CurrentId());
 
       // The ObserverList could have been removed already.  In fact, it could
-      // have been removed and then re-added!  If the master list's loop
+      // have been removed and then re-added!  If the master list's task runner
       // does not match this one, then we do not need to finish this
       // notification.
       if (it == observer_lists_.end() || it->second != context)