Revert of Explicitly suppress scrolling for wheel events that will trigger zooming

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 1315 matching lines @@
       browser_plugin_embedder_->HandleKeyboardEvent(event)) {
     return;
   }
   if (delegate_)
     delegate_->HandleKeyboardEvent(this, event);
 }
 
 bool WebContentsImpl::HandleWheelEvent(
     const blink::WebMouseWheelEvent& event) {
 #if !defined(OS_MACOSX)
-  // On platforms other than Mac, control+mousewheel may change zoom. On Mac,
-  // this isn't done for two reasons:
+  // On platforms other than Mac, control+mousewheel changes zoom. On Mac, this
+  // isn't done for two reasons:
   //   -the OS already has a gesture to do this through pinch-zoom
   //   -if a user starts an inertial scroll, let's go, and presses control
   //      (i.e. control+tab) then the OS's buffered scroll events will come in
   //      with control key set which isn't what the user wants
-  if (delegate_ && event.wheelTicksY &&
+  if (delegate_ &&
+      event.wheelTicksY &&
       (event.modifiers & blink::WebInputEvent::ControlKey) &&
-      !event.canScroll) {
+      // Avoid adjusting the zoom in response to two-finger-scrolling touchpad
+      // gestures, which are regrettably easy to trigger accidentally.
+      !event.hasPreciseScrollingDeltas) {
     delegate_->ContentsZoomChange(event.wheelTicksY > 0);
     return true;
   }
 #endif
   return false;
 }
 
 bool WebContentsImpl::PreHandleGestureEvent(
     const blink::WebGestureEvent& event) {
   return delegate_ && delegate_->PreHandleGestureEvent(this, event);
@@ skipping 3020 matching lines @@
   node->render_manager()->ResumeResponseDeferredAtStart();
 }
 
 void WebContentsImpl::SetForceDisableOverscrollContent(bool force_disable) {
   force_disable_overscroll_content_ = force_disable;
   if (view_)
     view_->SetOverscrollControllerEnabled(CanOverscrollContent());
 }
 
 }  // namespace content