Set default pinch viewport overlay scrollbar thickness in WebPreferences.

content/browser/web_contents/web_contents_impl.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/web_contents/web_contents_impl.h"
 
 #include <utility>
 
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
@@ skipping 534 matching lines @@
   prefs.lazy_layout_enabled =
       command_line.HasSwitch(switches::kEnableExperimentalWebKitFeatures);
   prefs.region_based_columns_enabled =
       command_line.HasSwitch(switches::kEnableRegionBasedColumns);
   prefs.threaded_html_parser =
       !command_line.HasSwitch(switches::kDisableThreadedHTMLParser);
   prefs.experimental_websocket_enabled =
       command_line.HasSwitch(switches::kEnableExperimentalWebSocket);
   prefs.pinch_virtual_viewport_enabled =
       command_line.HasSwitch(cc::switches::kEnablePinchVirtualViewport);
+  prefs.pinch_overlay_scrollbar_thickness = 10;

[jamesr, 2013/06/21 19:11:36]

if we don't have pinch viewport enabled, why set the thickness?

 
 #if defined(OS_ANDROID)
   prefs.user_gesture_required_for_media_playback = !command_line.HasSwitch(
       switches::kDisableGestureRequirementForMediaPlayback);
 #endif
 
   bool touch_device_present = false;
   touch_device_present = ui::IsTouchDevicePresent();
   const std::string touch_enabled_switch =
       command_line.HasSwitch(switches::kTouchEvents) ?
@@ skipping 3104 matching lines @@
 }
 
 BrowserPluginGuestManager*
     WebContentsImpl::GetBrowserPluginGuestManager() const {
   return static_cast<BrowserPluginGuestManager*>(
       GetBrowserContext()->GetUserData(
           browser_plugin::kBrowserPluginGuestManagerKeyName));
 }
 
 }  // namespace content