content: Add heartbeat trace for CategorizedWorkerPool.

base/synchronization/condition_variable.h

Index: base/synchronization/condition_variable.h
diff --git a/base/synchronization/condition_variable.h b/base/synchronization/condition_variable.h
index ebf90d249a33954bfaca75d3634523a58f112aef..b00f2bf025383cd616f0981965cd74964bb6707b 100644
--- a/base/synchronization/condition_variable.h
+++ b/base/synchronization/condition_variable.h
@@ -93,7 +93,8 @@ class BASE_EXPORT ConditionVariable {
   // Wait() releases the caller's critical section atomically as it starts to
   // sleep, and the reacquires it when it is signaled.
   void Wait();
-  void TimedWait(const TimeDelta& max_time);
+  // TimedWait() returns true on timeout, otherwise returns false.
+  bool TimedWait(const TimeDelta& max_time);
 
   // Broadcast() revives all waiting threads.
   void Broadcast();