Fix OverscrollWindowDelegate to not dispatch superfluous OverscrollModeChange events

content/browser/web_contents/aura/overscroll_window_delegate.cc

 // Copyright 2015 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/browser/web_contents/aura/overscroll_window_delegate.h"
 
 #include "base/i18n/rtl.h"
 #include "content/browser/frame_host/navigation_controller_impl.h"
 #include "content/browser/frame_host/navigation_entry_impl.h"
 #include "content/browser/renderer_host/overscroll_controller_delegate.h"
@@ skipping 25 matching lines @@
 void OverscrollWindowDelegate::StartOverscroll() {
   OverscrollMode old_mode = overscroll_mode_;
   if (delta_x_ > 0)
     overscroll_mode_ = OVERSCROLL_EAST;
   else
     overscroll_mode_ = OVERSCROLL_WEST;
   delegate_->OnOverscrollModeChange(old_mode, overscroll_mode_);
 }
 
 void OverscrollWindowDelegate::ResetOverscroll() {
+  if (overscroll_mode_ == OVERSCROLL_NONE)
+    return;
   delegate_->OnOverscrollModeChange(overscroll_mode_, OVERSCROLL_NONE);
   overscroll_mode_ = OVERSCROLL_NONE;
   delta_x_ = 0;
 }
 
 void OverscrollWindowDelegate::CompleteOrResetOverscroll() {
   if (overscroll_mode_ == OVERSCROLL_NONE)
     return;
   int width = delegate_->GetVisibleBounds().width();
   float ratio = (fabs(delta_x_)) / width;
@@ skipping 64 matching lines @@
       ResetOverscroll();
       break;
 
     default:
       break;
   }
   event->SetHandled();
 }
 
 }  // namespace content