Revert of base: Remove use of MessageLoopProxy

base/trace_event/trace_event_memory.h

Index: base/trace_event/trace_event_memory.h
diff --git a/base/trace_event/trace_event_memory.h b/base/trace_event/trace_event_memory.h
index e2b3ae93060ade693c67a6717113f2ab9e42ebe9..8e70020a0896debe59ed2ada0e8c23acc5ef710a 100644
--- a/base/trace_event/trace_event_memory.h
+++ b/base/trace_event/trace_event_memory.h
@@ -20,7 +20,7 @@
 
 namespace base {
 
-class SingleThreadTaskRunner;
+class MessageLoopProxy;
 
 namespace trace_event {
 
@@ -35,14 +35,15 @@
   typedef void (*HeapProfilerStopFunction)();
   typedef char* (*GetHeapProfileFunction)();
 
-  // |task_runner| must be a task runner for the primary thread for the client
+  // |message_loop_proxy| must be a proxy to the primary thread for the client
   // process, e.g. the UI thread in a browser. The function pointers must be
   // pointers to tcmalloc heap profiling functions; by avoiding direct calls to
   // these functions we avoid a dependency on third_party/tcmalloc from base.
-  TraceMemoryController(scoped_refptr<SingleThreadTaskRunner> task_runner,
-                        HeapProfilerStartFunction heap_profiler_start_function,
-                        HeapProfilerStopFunction heap_profiler_stop_function,
-                        GetHeapProfileFunction get_heap_profile_function);
+  TraceMemoryController(
+      scoped_refptr<MessageLoopProxy> message_loop_proxy,
+      HeapProfilerStartFunction heap_profiler_start_function,
+      HeapProfilerStopFunction heap_profiler_stop_function,
+      GetHeapProfileFunction get_heap_profile_function);
   virtual ~TraceMemoryController();
 
   // base::trace_event::TraceLog::EnabledStateChangedObserver overrides:
@@ -64,7 +65,7 @@
   bool IsTimerRunningForTest() const;
 
   // Ensures the observer starts and stops tracing on the primary thread.
-  scoped_refptr<SingleThreadTaskRunner> task_runner_;
+  scoped_refptr<MessageLoopProxy> message_loop_proxy_;
 
   // Pointers to tcmalloc heap profiling functions. Allows this class to use
   // tcmalloc functions without introducing a dependency from base to tcmalloc.