Revert of Remove enable/disable wheel gestures setting.

content/browser/renderer_host/render_widget_host_view_mac.mm

 // 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_mac.h"
 
 #import <objc/runtime.h>
 #include <OpenGL/gl.h>
 #include <QuartzCore/QuartzCore.h>
 #include <stdint.h>
@@ skipping 34 matching lines @@
 #include "content/browser/renderer_host/render_view_host_impl.h"
 #include "content/browser/renderer_host/render_widget_helper.h"
 #include "content/browser/renderer_host/render_widget_host_delegate.h"
 #include "content/browser/renderer_host/render_widget_host_input_event_router.h"
 #import "content/browser/renderer_host/render_widget_host_view_mac_dictionary_helper.h"
 #import "content/browser/renderer_host/render_widget_host_view_mac_editcommand_helper.h"
 #include "content/browser/renderer_host/resize_lock.h"
 #import "content/browser/renderer_host/text_input_client_mac.h"
 #include "content/common/accessibility_messages.h"
 #include "content/common/edit_command.h"
+#include "content/common/input/input_event_utils.h"
 #include "content/common/input_messages.h"
 #include "content/common/site_isolation_policy.h"
 #include "content/common/text_input_state.h"
 #include "content/common/view_messages.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/browser_plugin_guest_manager.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/native_web_keyboard_event.h"
 #include "content/public/browser/render_widget_host_view_frame_subscriber.h"
 #import "content/public/browser/render_widget_host_view_mac_delegate.h"
@@ skipping 490 matching lines @@
                                                  bool is_guest_view_hack)
     : render_widget_host_(RenderWidgetHostImpl::From(widget)),
       text_input_type_(ui::TEXT_INPUT_TYPE_NONE),
       can_compose_inline_(true),
       browser_compositor_state_(BrowserCompositorDestroyed),
       browser_compositor_placeholder_(new BrowserCompositorMacPlaceholder),
       page_at_minimum_scale_(true),
       is_loading_(false),
       allow_pause_for_resize_or_repaint_(true),
       is_guest_view_hack_(is_guest_view_hack),
+      wheel_gestures_enabled_(UseGestureBasedWheelScrolling()),
       fullscreen_parent_host_view_(nullptr),
       begin_frame_source_(nullptr),
       needs_begin_frames_(false),
       weak_factory_(this) {
   // |cocoa_view_| owns us and we will be deleted when |cocoa_view_|
   // goes away.  Since we autorelease it, our caller must put
   // |GetNativeView()| into the view hierarchy right after calling us.
   cocoa_view_ = [[[RenderWidgetHostViewCocoa alloc]
                   initWithRenderWidgetHostViewMac:this] autorelease];
 
@@ skipping 993 matching lines @@
   mouse_locked_ = false;
 
   // Unlock position of mouse cursor and unhide it.
   CGAssociateMouseAndMouseCursorPosition(YES);
   [NSCursor unhide];
 
   if (render_widget_host_)
     render_widget_host_->LostMouseLock();
 }
 
+void RenderWidgetHostViewMac::WheelEventAck(
+    const blink::WebMouseWheelEvent& event,
+    InputEventAckState ack_result) {
+  // TODO(dtapuska): Remove this handling of the wheel event ack
+  // once wheel gestures is enabled for a full release; see crbug.com/598798.
+  if (wheel_gestures_enabled_)
+    return;
+  bool consumed = ack_result == INPUT_EVENT_ACK_STATE_CONSUMED;
+  // Only record a wheel event as unhandled if JavaScript handlers got a chance
+  // to see it (no-op wheel events are ignored by the event dispatcher)
+  if (event.deltaX || event.deltaY)
+    [cocoa_view_ processedWheelEvent:event consumed:consumed];
+}
+
 void RenderWidgetHostViewMac::GestureEventAck(
     const blink::WebGestureEvent& event,
     InputEventAckState ack_result) {
   if (!wheel_gestures_enabled_)
     return;
   bool consumed = ack_result == INPUT_EVENT_ACK_STATE_CONSUMED;
   switch (event.type) {
     case blink::WebInputEvent::GestureScrollBegin:
     case blink::WebInputEvent::GestureScrollUpdate:
     case blink::WebInputEvent::GestureScrollEnd:
@@ skipping 1856 matching lines @@
 
 // "-webkit-app-region: drag | no-drag" is implemented on Mac by excluding
 // regions that are not draggable. (See ControlRegionView in
 // native_app_window_cocoa.mm). This requires the render host view to be
 // draggable by default.
 - (BOOL)mouseDownCanMoveWindow {
   return YES;
 }
 
 @end