Add canExceedIdleDeadlineIfRequired function to Scheduler and use it in Oilpan

public/platform/WebScheduler.h

Index: public/platform/WebScheduler.h
diff --git a/public/platform/WebScheduler.h b/public/platform/WebScheduler.h
index a2cda3eac91603b1f741794377d01c942d88d16e..85d6778e49e855550f307ffd25a27a95dc862e30 100644
--- a/public/platform/WebScheduler.h
+++ b/public/platform/WebScheduler.h
@@ -35,6 +35,16 @@ public:
     // 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.