Revert everything related to the relanding.

base/message_loop.h

Index: base/message_loop.h
diff --git a/base/message_loop.h b/base/message_loop.h
index 35b2651d85b0d1d9bcbffac0b6b0109dfe027d02..8deacecd10d293a857ed736809549dee8baa5903 100644
--- a/base/message_loop.h
+++ b/base/message_loop.h
@@ -9,10 +9,11 @@
 #include <string>
 
 #include "base/basictypes.h"
-#include "base/lock.h"
+#include "base/histogram.h"
 #include "base/message_pump.h"
 #include "base/observer_list.h"
 #include "base/ref_counted.h"
+#include "base/scoped_ptr.h"
 #include "base/task.h"
 
 #if defined(OS_WIN)
@@ -26,8 +27,6 @@
 #endif
 #endif
 
-class Histogram;
-
 // A MessageLoop is used to process events for a particular thread.  There is
 // at most one MessageLoop instance per thread.
 //
@@ -428,6 +427,9 @@ class MessageLoop : public base::MessagePump::Delegate {
   // If message_histogram_ is NULL, this is a no-op.
   void HistogramEvent(int event);
 
+  static const LinearHistogram::DescriptionPair event_descriptions_[];
+  static bool enable_histogrammer_;
+
   Type type_;
 
   // A list of tasks that need to be processed by this instance.  Note that