Revert of Remove enable/disable wheel gestures setting.

content/browser/renderer_host/render_widget_host_view_mac_unittest.mm

Index: content/browser/renderer_host/render_widget_host_view_mac_unittest.mm
diff --git a/content/browser/renderer_host/render_widget_host_view_mac_unittest.mm b/content/browser/renderer_host/render_widget_host_view_mac_unittest.mm
index e142fdcfd2e836e163b78503aef5e095a9cc5c15..2fe2635b49669f80aeaa6a708ff2d097bffa8617 100644
--- a/content/browser/renderer_host/render_widget_host_view_mac_unittest.mm
+++ b/content/browser/renderer_host/render_widget_host_view_mac_unittest.mm
@@ -266,6 +266,19 @@
     RenderViewHostImplTestHarness::TearDown();
   }
 
+  void SetupForWheelGestures(bool enable_wheel_gestures) {
+    CHECK(!base::CommandLine::ForCurrentProcess()->HasSwitch(
+        switches::kDisableWheelGestures));
+    CHECK(!base::CommandLine::ForCurrentProcess()->HasSwitch(
+        switches::kEnableWheelGestures));
+    base::CommandLine::ForCurrentProcess()->AppendSwitch(
+        enable_wheel_gestures ? switches::kEnableWheelGestures
+                              : switches::kDisableWheelGestures);
+    // Owned by its |cocoa_view()|, i.e. |rwhv_cocoa_|.
+    rwhv_mac_ = new RenderWidgetHostViewMac(rvh()->GetWidget(), false);
+    rwhv_cocoa_.reset([rwhv_mac_->cocoa_view() retain]);
+  }
+
   void RecycleAndWait() {
     pool_.Recycle();
     base::MessageLoop::current()->RunUntilIdle();
@@ -920,8 +933,66 @@
   host->ShutdownAndDestroyWidget(true);
 }
 
+TEST_F(RenderWidgetHostViewMacTest, IgnoreEmptyUnhandledWheelEvent) {
+  SetupForWheelGestures(false);
+
+  // Initialize the view associated with a MockRenderWidgetHostImpl, rather than
+  // the MockRenderProcessHost that is set up by the test harness which mocks
+  // out |OnMessageReceived()|.
+  TestBrowserContext browser_context;
+  MockRenderProcessHost* process_host =
+      new MockRenderProcessHost(&browser_context);
+  process_host->Init();
+  MockRenderWidgetHostDelegate delegate;
+  int32_t routing_id = process_host->GetNextRoutingID();
+  MockRenderWidgetHostImpl* host =
+      new MockRenderWidgetHostImpl(&delegate, process_host, routing_id);
+  RenderWidgetHostViewMac* view = new RenderWidgetHostViewMac(host, false);
+  process_host->sink().ClearMessages();
+
+  // Add a delegate to the view.
+  base::scoped_nsobject<MockRenderWidgetHostViewMacDelegate> view_delegate(
+      [[MockRenderWidgetHostViewMacDelegate alloc] init]);
+  view->SetDelegate(view_delegate.get());
+
+  // Send an initial wheel event for scrolling by 3 lines.
+  NSEvent* event1 = MockScrollWheelEventWithPhase(@selector(phaseBegan), 3);
+  [view->cocoa_view() scrollWheel:event1];
+  ASSERT_EQ(1U, process_host->sink().message_count());
+  process_host->sink().ClearMessages();
+
+  // Indicate that the wheel event was unhandled.
+  InputEventAck unhandled_ack(blink::WebInputEvent::MouseWheel,
+                              INPUT_EVENT_ACK_STATE_NOT_CONSUMED);
+  std::unique_ptr<IPC::Message> response1(
+      new InputHostMsg_HandleInputEvent_ACK(0, unhandled_ack));
+  host->OnMessageReceived(*response1);
+
+  // Check that the view delegate got an unhandled wheel event.
+  ASSERT_EQ(YES, view_delegate.get().unhandledWheelEventReceived);
+  view_delegate.get().unhandledWheelEventReceived = NO;
+
+  // Send another wheel event, this time for scrolling by 0 lines (empty event).
+  NSEvent* event2 = MockScrollWheelEventWithPhase(@selector(phaseChanged), 0);
+  [view->cocoa_view() scrollWheel:event2];
+  ASSERT_EQ(1U, process_host->sink().message_count());
+
+  // Indicate that the wheel event was also unhandled.
+  std::unique_ptr<IPC::Message> response2(
+      new InputHostMsg_HandleInputEvent_ACK(0, unhandled_ack));
+  host->OnMessageReceived(*response2);
+
+  // Check that the view delegate ignored the empty unhandled wheel event.
+  ASSERT_EQ(NO, view_delegate.get().unhandledWheelEventReceived);
+
+  // Clean up.
+  host->ShutdownAndDestroyWidget(true);
+}
+
 TEST_F(RenderWidgetHostViewMacTest,
        IgnoreEmptyUnhandledWheelEventWithWheelGestures) {
+  SetupForWheelGestures(true);
+
   // Initialize the view associated with a MockRenderWidgetHostImpl, rather than
   // the MockRenderProcessHost that is set up by the test harness which mocks
   // out |OnMessageReceived()|.