Add instrumentation to the MessagePumpMac family of classes.

base/message_loop/message_pump.h

Index: base/message_loop/message_pump.h
diff --git a/base/message_loop/message_pump.h b/base/message_loop/message_pump.h
index 0ebba3a3e60ccfd07abb2808e2632a254a76747c..816bb3c3d39eb88097731ad9cc2e4178c4ae1a63 100644
--- a/base/message_loop/message_pump.h
+++ b/base/message_loop/message_pump.h
@@ -6,10 +6,12 @@
 #define BASE_MESSAGE_LOOP_MESSAGE_PUMP_H_
 
 #include "base/base_export.h"
+#include "base/basictypes.h"
 #include "base/threading/non_thread_safe.h"
 
 namespace base {
 
+class TimeDelta;
 class TimeTicks;
 
 class BASE_EXPORT MessagePump : public NonThreadSafe {
@@ -39,6 +41,19 @@ class BASE_EXPORT MessagePump : public NonThreadSafe {
     // Called from within Run just before the message pump goes to sleep.
     // Returns true to indicate that idle work was done.
     virtual bool DoIdleWork() = 0;
+
+    // Via the two required out pointers, returns the length of the Delegate's
+    // work queue and the length of time that the first item in the queue has
+    // been waiting to run. If the work queue is empty, the count and delay
+    // will both be zero.
+    // Note that this only counts the tasks in the ready-to-run queue and not
+    // the incoming queue that is used by other threads to post tasks. The
+    // latter queue requires holding a lock, which is deemed too expensive for
+    // instrumentation code. Under normal conditions, the incoming queue should
+    // be small or zero, but under heavy loads it may be much larger and
+    // |queue_count| may be up to 1/4 the size of the incoming queue.
+    virtual void GetQueueingInformation(size_t* queue_count,
+                                        TimeDelta* queueing_delay) {}
   };
 
   MessagePump();