Fix mouse wheel scrolling on PDFs.

content/renderer/render_view_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/renderer/render_view_impl.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/auto_reset.h"
@@ skipping 1095 matching lines @@
   settings->setPinchOverlayScrollbarThickness(
       prefs.pinch_overlay_scrollbar_thickness);
   settings->setUseSolidColorScrollbars(prefs.use_solid_color_scrollbars);
 
   settings->setShowContextMenuOnMouseUp(prefs.context_menu_on_mouse_up);
 
 #if defined(OS_MACOSX)
   settings->setDoubleTapToZoomEnabled(true);
   web_view->setMaximumLegibleScale(prefs.default_maximum_page_scale_factor);
 #endif
+
+  settings->setWheelGesturesEnabled(UseGestureBasedWheelScrolling());
 }
 
 /*static*/
 RenderViewImpl* RenderViewImpl::Create(CompositorDependencies* compositor_deps,
                                        const ViewMsg_New_Params& params,
                                        bool was_created_by_renderer) {
   DCHECK(params.view_id != MSG_ROUTING_NONE);
   RenderViewImpl* render_view = NULL;
   if (g_create_render_view_impl)
     render_view = g_create_render_view_impl(compositor_deps, params);
@@ skipping 2313 matching lines @@
   if (IsUseZoomForDSFEnabled()) {
     webview()->setZoomFactorForDeviceScaleFactor(device_scale_factor_);
   } else {
     webview()->setDeviceScaleFactor(device_scale_factor_);
   }
   webview()->settings()->setPreferCompositingToLCDTextEnabled(
       PreferCompositingToLCDText(compositor_deps_, device_scale_factor_));
 }
 
 }  // namespace content