Add canExceedIdleDeadlineIfRequired function to Scheduler and use it in Oilpan

public/platform/WebScheduler.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef WebScheduler_h
 #define WebScheduler_h
 
 #include "WebCommon.h"
 #include "public/platform/WebThread.h"
 
@@ skipping 17 matching lines @@
 
     // Called during Blink's shutdown to delete any pending tasks from the
     // scheduler. Must be called on the main thread.
     virtual void shutdown() { }
 
     // Returns true if there is high priority work pending on the main thread
     // and the caller should yield to let the scheduler service that work.
     // Must be called on the main thread.
     virtual bool shouldYieldForHighPriorityWork() { return false; }
 
+    // Returns true if a currently running idle task could exceed its deadline
+    // without impacting user experience too much. This should only be used if
+    // there is a task which cannot be pre-empted and is likely to take longer
+    // than the largest expected idle task deadline. It should NOT be polled to
+    // check whether more work can be performed on the current idle task after
+    // its deadline has expired - post a new idle task for the continuation of
+    // the work in this case.
+    // Must be called from the main thread.
+    virtual bool canExceedIdleDeadlineIfRequired() { return false; }
+
     // Schedule an idle task to run the Blink main thread. For non-critical
     // tasks which may be reordered relative to other task types and may be
     // starved for an arbitrarily long time if no idle time is available.
     // Takes ownership of |IdleTask|. Can be called from any thread.
     virtual void postIdleTask(const WebTraceLocation&, IdleTask*) { }
 
     // Like postIdleTask but does not run the idle task until after some other
     // task has run. This enables posting of a task which won't stop the Blink
     // main thread from sleeping, but will start running after it wakes up.
     // Takes ownership of |IdleTask|. Can be called from any thread.
     virtual void postIdleTaskAfterWakeup(const WebTraceLocation&, IdleTask*) { }
 
     // Schedule a loading task to be run on the Blink main thread. Loading
     // tasks usually have the default priority, but may be deprioritised
     // when the user is interacting with the device.
     // Takes ownership of |WebThread::Task|. Can be called from any thread.
     virtual void postLoadingTask(const WebTraceLocation&, WebThread::Task*) { }
 };
 
 } // namespace blink
 
 #endif // WebScheduler_h