Add instrumentation to the MessagePumpMac family of classes.

This adds UMA-uploaded histograms of sampling intervals for key points of data:
* Total time spent in a CFRunLoop
* Total time waiting in CFRunLoop
* Total time servicing MessagePump::Delegate (the MessageLoop)
* The MessageLoop queue size and queueing delay before servicing

It adds 1 second sampling for 15 seconds at startup, only for the main thread
(NSApplication-based) run loops.

The data will be used to determine if adding scheduling-like behavior to the
MessagePump will result in more efficient processing of the MessageLoop work.

An unforunate side effect of this change is exposing another method on the
MessagePump::Delegate interface, but there does not appear to be a better way
to do this.

BUG=264886
R=jar@chromium.org, mark@chromium.org

Review URL: https://codereview.chromium.org/22911026

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221427 0039d316-1c4b-4281-b951-d872f2087c98

base/message_loop/message_loop.cc

@@ -660,6 +660,20 @@ bool MessageLoop::DoIdleWork() {
   return false;
 }
 
+void MessageLoop::GetQueueingInformation(size_t* queue_size,
+                                         TimeDelta* queueing_delay) {
+  *queue_size = work_queue_.size();
+  if (*queue_size == 0) {
+    *queueing_delay = TimeDelta();
+    return;
+  }
+
+  const PendingTask& next_to_run = work_queue_.front();
+  tracked_objects::Duration duration =
+      tracked_objects::TrackedTime::Now() - next_to_run.EffectiveTimePosted();
+  *queueing_delay = TimeDelta::FromMilliseconds(duration.InMilliseconds());
+}
+
 void MessageLoop::DeleteSoonInternal(const tracked_objects::Location& from_here,
                                      void(*deleter)(const void*),
                                      const void* object) {

base/message_loop/message_loop.h

@@ -478,6 +478,8 @@ class BASE_EXPORT MessageLoop : public MessagePump::Delegate {
   virtual bool DoWork() OVERRIDE;
   virtual bool DoDelayedWork(TimeTicks* next_delayed_work_time) OVERRIDE;
   virtual bool DoIdleWork() OVERRIDE;
+  virtual void GetQueueingInformation(size_t* queue_size,
+                                      TimeDelta* queueing_delay) OVERRIDE;
 
   Type type_;
 

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();

base/message_loop/message_pump_mac.h

@@ -36,6 +36,8 @@
 
 #include <CoreFoundation/CoreFoundation.h>
 
+#include "base/memory/weak_ptr.h"
+
 #if !defined(__OBJC__)
 class NSAutoreleasePool;
 #else  // !defined(__OBJC__)
@@ -57,6 +59,7 @@ class NSAutoreleasePool;
 
 namespace base {
 
+class MessagePumpInstrumentation;
 class RunLoop;
 class TimeTicks;
 
@@ -93,6 +96,11 @@ class MessagePumpCFRunLoopBase : public MessagePump {
   // objects autoreleased by work to fall into the current autorelease pool.
   virtual NSAutoreleasePool* CreateAutoreleasePool();
 
+  // Enables instrumentation of the MessagePump. See MessagePumpInstrumentation
+  // in the implementation for details.
+  void EnableInstrumentation();
+  WeakPtr<MessagePumpInstrumentation> instrumentation_;
+
  private:
   // Timer callback scheduled by ScheduleDelayedWork.  This does not do any
   // work, but it signals work_source_ so that delayed work can be performed
@@ -106,11 +114,11 @@ class MessagePumpCFRunLoopBase : public MessagePump {
   static void RunWorkSource(void* info);
   bool RunWork();
 
-  // Perform idle-priority work.  This is normally called by PreWaitObserver,
-  // but is also associated with idle_work_source_.  When this function
-  // actually does perform idle work, it will resignal that source.  The
-  // static method calls the instance method; the instance method returns
-  // true if idle work was done.
+  // Perform idle-priority work.  This is normally called by
+  // StartOrEndWaitObserver, but is also associated with idle_work_source_. When
+  // this function actually does perform idle work, it will resignal that
+  // source.  The static method calls the instance method; the instance method
+  // returns true if idle work was done.
   static void RunIdleWorkSource(void* info);
   bool RunIdleWork();
 
@@ -132,7 +140,7 @@ class MessagePumpCFRunLoopBase : public MessagePump {
 
   // Observer callback responsible for performing idle-priority work, before
   // the run loop goes to sleep.  Associated with idle_work_observer_.
-  static void PreWaitObserver(CFRunLoopObserverRef observer,
+  static void StartOrEndWaitObserver(CFRunLoopObserverRef observer,
                                      CFRunLoopActivity activity, void* info);
 
   // Observer callback called before the run loop processes any sources.