Prevent ctrl+2f scroll on the touchpad to zoom the page

content/browser/renderer_host/render_widget_host_view_aura.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/render_widget_host_view_aura.h"
 
 #include "base/auto_reset.h"
 #include "base/basictypes.h"
 #include "base/bind.h"
 #include "base/callback_helpers.h"
@@ skipping 2847 matching lines @@
     return;
 
   if (event->type() == ui::ET_SCROLL) {
     if (event->finger_count() != 2)
       return;
     blink::WebGestureEvent gesture_event =
         MakeWebGestureEventFlingCancel();
     host_->ForwardGestureEvent(gesture_event);
     blink::WebMouseWheelEvent mouse_wheel_event =
         MakeWebMouseWheelEvent(event);
+
+    // We don't want ctrl+two finger scroll to trigger the WebContents zooming
+    // function as it is too sensitive and most people don't expect the effect
+    // (unlike ctrl+mousewheel, which most people expect to zoom the page).
+    // Therefore, we clear the modifier here if and only if the ctrl key is
+    // pressed and no any other key is pressed at the same time. This prevents
+    // WebContentsImpl to zoom the page while retain the scroll event and other

[Daniel Erat, 2013/12/26 14:44:22]

nit: s/to zoom/from zooming/, s/while retain/while retaining/

[Shecky Lin, 2013/12/27 03:23:54]

Done.

+    // modifier combinations in case the webpage might want to use them.
+    if (mouse_wheel_event.modifiers == blink::WebInputEvent::ControlKey)
+      mouse_wheel_event.modifiers = 0;
     host_->ForwardWheelEvent(mouse_wheel_event);
     RecordAction(UserMetricsAction("TrackpadScroll"));
   } else if (event->type() == ui::ET_SCROLL_FLING_START ||
              event->type() == ui::ET_SCROLL_FLING_CANCEL) {
     blink::WebGestureEvent gesture_event =
         MakeWebGestureEvent(event);
     host_->ForwardGestureEvent(gesture_event);
     if (event->type() == ui::ET_SCROLL_FLING_START)
       RecordAction(UserMetricsAction("TrackpadScrollFling"));
   }
@@ skipping 608 matching lines @@
     RenderWidgetHost* widget) {
   return new RenderWidgetHostViewAura(widget);
 }
 
 // static
 void RenderWidgetHostViewPort::GetDefaultScreenInfo(WebScreenInfo* results) {
   GetScreenInfoForWindow(results, NULL);
 }
 
 }  // namespace content