cc: Avoid posting renewTreePriority tasks with negative delay.

BUG=175935
NOTRY=True

Review URL: https://chromiumcodereview.appspot.com/12255014

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@182314 0039d316-1c4b-4281-b951-d872f2087c98

cc/thread_proxy.cc

@@ -1191,16 +1191,16 @@ void ThreadProxy::renewTreePriority()
             priority == SMOOTHNESS_TAKES_PRIORITY);
     }
 
+    base::TimeDelta delay = m_smoothnessTakesPriorityExpirationTime -
+        base::TimeTicks::Now();
+
     // Need to make sure a delayed task is posted when we have smoothness
     // takes priority expiration time in the future.
-    if (m_smoothnessTakesPriorityExpirationTime <= base::TimeTicks::Now())
+    if (delay <= base::TimeDelta())
         return;
     if (m_renewTreePriorityOnImplThreadPending)
         return;
 
-    base::TimeDelta delay = m_smoothnessTakesPriorityExpirationTime -
-        base::TimeTicks::Now();
-
     Proxy::implThread()->postDelayedTask(
         base::Bind(&ThreadProxy::renewTreePriorityOnImplThread,
                    m_weakFactoryOnImplThread.GetWeakPtr()),