Add trace code to track all posted tasks in message_loop.

base/debug/trace_event.h

Index: base/debug/trace_event.h
diff --git a/base/debug/trace_event.h b/base/debug/trace_event.h
index e7b3f90066ac8631099d0f39a8558ec517b7f810..61ffebc19170d158054166928f9242b526156ba9 100644
--- a/base/debug/trace_event.h
+++ b/base/debug/trace_event.h
@@ -141,6 +141,22 @@
   INTERNAL_TRACE_EVENT_ADD_SCOPED( \
       category, name, arg1_name, arg1_val, arg2_name, arg2_val)
 
+// Same as TRACE_EVENT except that they are not included in official builds.
+#ifdef OFFICIAL_BUILD
+#define UNSHIPPED_TRACE_EVENT0(category, name) (void)0
+#define UNSHIPPED_TRACE_EVENT1(category, name, arg1_name, arg1_val) (void)0
+#define UNSHIPPED_TRACE_EVENT2(category, name, arg1_name, arg1_val, \
+                               arg2_name, arg2_val) (void)0
+#else
+#define UNSHIPPED_TRACE_EVENT0(category, name) \
+  TRACE_EVENT0(category, name)
+#define UNSHIPPED_TRACE_EVENT1(category, name, arg1_name, arg1_val) \
+  TRACE_EVENT1(category, name, arg1_name, arg1_val)
+#define UNSHIPPED_TRACE_EVENT2(category, name, arg1_name, arg1_val, \
+                               arg2_name, arg2_val) \
+  TRACE_EVENT2(category, name, arg1_name, arg1_val, arg2_name, arg2_val)
+#endif
+
 // Records a single event called "name" immediately, with 0, 1 or 2
 // associated arguments. If the category is not enabled, then this
 // does nothing.
@@ -577,6 +593,9 @@ class BASE_EXPORT TraceLog {
 
   // Exposed for unittesting:
 
+  // Allows deleting our singleton instance.
+  static void DeleteForTesting();
+
   // Allows resurrecting our singleton instance post-AtExit processing.
   static void Resurrect();