Refactor TimeBase to post tasks. Workers to use real Idle tasks.

Source/core/workers/WorkerThread.h

Index: Source/core/workers/WorkerThread.h
diff --git a/Source/core/workers/WorkerThread.h b/Source/core/workers/WorkerThread.h
index 4a66960a7817ce0179f3d486e3edebeab2ac84a6..9adf5bee89a42a3a2382540f75c108d5aafc618e 100644
--- a/Source/core/workers/WorkerThread.h
+++ b/Source/core/workers/WorkerThread.h
@@ -47,7 +47,6 @@ class WebWaitableEvent;
 class WorkerGlobalScope;
 class WorkerInspectorController;
 class WorkerReportingProxy;
-class WorkerSharedTimer;
 class WorkerThreadShutdownFinishTask;
 class WorkerThreadStartupData;
 class WorkerThreadTask;
@@ -122,16 +121,33 @@ protected:
     virtual void destroyIsolate();
     virtual void terminateV8Execution();
 
+    // This is protected virtual for testing.
+    virtual bool doIdleGc(double deadlineSeconds);
+
+    WebThreadSupportingGC* threadForTesting() const
+    {
+        return m_thread.get();
+    }
+
+    void setMinQuietPeriodBeforeDoingIdleGcForTesting(long long minQuietPeriodBeforeDoingIdleGc)

[Sami, 2015/04/09 10:52:29]

For better or worse, "double seconds" is the preferred monotonic time data type
in Blink. I'm not sure why delays use long long but IMO that shouldn't be needed
here (feel free to keep in long long internally if you want). Also please make
the unit obvious in the function and parameter names.

[alex clarke (OOO till 29th), 2015/04/10 15:29:38]

Acknowledged.

+    {
+        m_minQuietPeriodMsBeforeDoingIdleGc = minQuietPeriodBeforeDoingIdleGc;
+    }
+
 private:
-    friend class WorkerSharedTimer;
+    friend class WorkerThreadIdleTask;
     friend class WorkerThreadShutdownFinishTask;
+    friend class WorkerThreadWaitUntilIdleTask;
+    friend class WorkerThreadWakeupIdleTask;
 
     void stopInShutdownSequence();
     void stopInternal();
 
     void initialize();
     void cleanup();
-    void idleHandler();
+    void dontStartIdleTaskYet();

[Sami, 2015/04/09 10:52:29]

Okay, I think I agree that it's probably better not to talk about idle periods
here. However the naming could be a little more consistent since you don't
"start" tasks but either "post" or "run" them. How about
dontPostIdleTaskYet()/maybePostIdleTask(), or better yet:
dontStartIdleGcYet()/maybeStartIdleGc()/idleGc()?

[alex clarke (OOO till 29th), 2015/04/10 15:29:37]

Acknowledged.

+    void maybeStartIdleTask();
+    void idleTask(double deadlineSeconds);
     void postDelayedTask(PassOwnPtr<ExecutionContextTask>, long long delayMs);
     void postDelayedTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>, long long delayMs);
 
@@ -158,6 +174,9 @@ private:
     // Used to signal thread termination.
     OwnPtr<WebWaitableEvent> m_terminationEvent;
 
+    long long m_minQuietPeriodMsBeforeDoingIdleGc;
+    bool m_dontStartIdleTaskYet;
+
     // FIXME: This has to be last because of crbug.com/401397 - the
     // WorkerThread might get deleted before it had a chance to properly
     // shut down. By deleting the WebThread first, we can guarantee that