Reenable the tap down gesture.

content/browser/renderer_host/input/gesture_event_filter_unittest.cc

Index: content/browser/renderer_host/input/gesture_event_filter_unittest.cc
diff --git a/content/browser/renderer_host/input/gesture_event_filter_unittest.cc b/content/browser/renderer_host/input/gesture_event_filter_unittest.cc
index 0234fd9340b8d05914b3debb9f8dab2bf0539988..971fcf1d5cb060bae9c9a4b38c810cdd931d39f0 100644
--- a/content/browser/renderer_host/input/gesture_event_filter_unittest.cc
+++ b/content/browser/renderer_host/input/gesture_event_filter_unittest.cc
@@ -570,8 +570,8 @@ INSTANTIATE_TEST_CASE_P(AllSources,
                                         WebGestureEvent::Touchpad));
 #endif  // GTEST_HAS_PARAM_TEST
 
-// Test that GestureShowPress events don't wait for ACKs.
-TEST_F(GestureEventFilterTest, GestureShowPressIgnoresAck) {
+// Test that GestureShowPress and GestureTapDown events don't wait for ACKs.
+TEST_F(GestureEventFilterTest, GestureShowPressAndTapDownIgnoreAck) {
   SimulateGestureEvent(WebInputEvent::GestureShowPress,
                        WebGestureEvent::Touchscreen);
 
@@ -588,7 +588,14 @@ TEST_F(GestureEventFilterTest, GestureShowPressIgnoresAck) {
                        WebGestureEvent::Touchscreen);
 
   EXPECT_EQ(1U, GetAndResetSentGestureEventCount());
-  // The show press events will have escaped the queue, since they ignore acks.
+  EXPECT_EQ(0U, GestureEventLastQueueEventSize());
+
+  SimulateGestureEvent(WebInputEvent::GestureTapDown,
+                       WebGestureEvent::Touchscreen);
+
+  EXPECT_EQ(1U, GetAndResetSentGestureEventCount());
+  // The show press and tap down events will have escaped the queue, since they
+  // ignore acks.
   EXPECT_EQ(0U, GestureEventLastQueueEventSize());
 }