Put vertical overscroll behind kScrollEndEffect flag

content/browser/renderer_host/overscroll_controller.cc

 // Copyright (c) 2012 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/renderer_host/overscroll_controller.h"
 
+#include "base/command_line.h"
 #include "base/logging.h"
 #include "content/browser/renderer_host/overscroll_controller_delegate.h"
 #include "content/public/browser/overscroll_configuration.h"
+#include "content/public/common/content_switches.h"
 
 using WebKit::WebInputEvent;
 
+namespace {
+
+bool IsScrollEndEffectEnabled() {
+  return CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+      switches::kScrollEndEffect) == "1";
+}
+
+}  // namespace
+
 namespace content {
 
 OverscrollController::OverscrollController()
     : overscroll_mode_(OVERSCROLL_NONE),
       scroll_state_(STATE_UNKNOWN),
       overscroll_delta_x_(0.f),
       overscroll_delta_y_(0.f),
       delegate_(NULL) {
 }
 
@@ skipping 272 matching lines @@
   // to make sure that subsequent scroll events go through to the page first.
   OverscrollMode new_mode = OVERSCROLL_NONE;
   const float kMinRatio = 2.5;
   if (fabs(overscroll_delta_x_) > horiz_threshold &&
       fabs(overscroll_delta_x_) > fabs(overscroll_delta_y_) * kMinRatio)
     new_mode = overscroll_delta_x_ > 0.f ? OVERSCROLL_EAST : OVERSCROLL_WEST;
   else if (fabs(overscroll_delta_y_) > vert_threshold &&
            fabs(overscroll_delta_y_) > fabs(overscroll_delta_x_) * kMinRatio)
     new_mode = overscroll_delta_y_ > 0.f ? OVERSCROLL_SOUTH : OVERSCROLL_NORTH;
 
+  // The vertical oversrcoll currently does not have any UX effects other then
+  // for the scroll end effect, so testing if it is enabled.
+  if ((new_mode == OVERSCROLL_SOUTH || new_mode == OVERSCROLL_NORTH) &&
+      !IsScrollEndEffectEnabled())
+    new_mode = OVERSCROLL_NONE;
+
   if (overscroll_mode_ == OVERSCROLL_NONE)
     SetOverscrollMode(new_mode);
   else if (new_mode != overscroll_mode_)
     SetOverscrollMode(OVERSCROLL_NONE);
 
   if (overscroll_mode_ == OVERSCROLL_NONE)
     return;
 
   // Tell the delegate about the overscroll update so that it can update
   // the display accordingly (e.g. show history preview etc.).
@@ skipping 37 matching lines @@
   overscroll_mode_ = mode;
   if (overscroll_mode_ == OVERSCROLL_NONE)
     overscroll_delta_x_ = overscroll_delta_y_ = 0.f;
   else
     scroll_state_ = STATE_OVERSCROLLING;
   if (delegate_)
     delegate_->OnOverscrollModeChange(old_mode, overscroll_mode_);
 }
 
 }  // namespace content