Add DCHECK for shared_timer_suspended_ which shouldn't be negative

content/child/blink_platform_impl.cc

 // 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.
 
 #include "content/child/blink_platform_impl.h"
 
 #include <math.h>
 
 #include <vector>
 
@@ skipping 884 matching lines @@
 #else
   return noDecodedImageByteLimit;
 #endif
 }
 
 void BlinkPlatformImpl::SuspendSharedTimer() {
   ++shared_timer_suspended_;
 }
 
 void BlinkPlatformImpl::ResumeSharedTimer() {
+  DCHECK_GT(shared_timer_suspended_, 0);
+
   // The shared timer may have fired or been adjusted while we were suspended.
   if (--shared_timer_suspended_ == 0 &&
       (!shared_timer_.IsRunning() ||
        shared_timer_fire_time_was_set_while_suspended_)) {
     shared_timer_fire_time_was_set_while_suspended_ = false;
     setSharedTimerFireInterval(
         shared_timer_fire_time_ - monotonicallyIncreasingTime());
   }
 }
 
 }  // namespace content