[Android] Enable input event stream validation

content/common/input/gesture_event_stream_validator.cc

Index: content/common/input/gesture_event_stream_validator.cc
diff --git a/content/common/input/gesture_event_stream_validator.cc b/content/common/input/gesture_event_stream_validator.cc
index a6229f98b6995fc3c3622e46e51108debbad41a9..b95a674541df1958e44fbf2b6b823758568abed6 100644
--- a/content/common/input/gesture_event_stream_validator.cc
+++ b/content/common/input/gesture_event_stream_validator.cc
@@ -24,8 +24,10 @@ bool GestureEventStreamValidator::Validate(const blink::WebGestureEvent& event,
   error_msg->clear();
   switch (event.type) {
     case WebInputEvent::GestureScrollBegin:
-      if (scrolling_ || pinching_)
+      if (scrolling_)
         error_msg->append("Scroll begin during scroll\n");
+      if (pinching_)
+        error_msg->append("Scroll begin during pinch\n");
       scrolling_ = true;
       break;
     case WebInputEvent::GestureScrollUpdate:
@@ -42,18 +44,16 @@ bool GestureEventStreamValidator::Validate(const blink::WebGestureEvent& event,
       scrolling_ = false;
       break;
     case WebInputEvent::GesturePinchBegin:
-      if (!scrolling_)
-        error_msg->append("Pinch begin outside of scroll\n");
       if (pinching_)
         error_msg->append("Pinch begin during pinch\n");
       pinching_ = true;
       break;
     case WebInputEvent::GesturePinchUpdate:
-      if (!pinching_ || !scrolling_)
+      if (!pinching_)
         error_msg->append("Pinch update outside of pinch\n");
       break;
     case WebInputEvent::GesturePinchEnd:
-      if (!pinching_ || !scrolling_)
+      if (!pinching_)
         error_msg->append("Pinch end outside of pinch\n");
       pinching_ = false;
       break;
@@ -64,11 +64,13 @@ bool GestureEventStreamValidator::Validate(const blink::WebGestureEvent& event,
       break;
     case WebInputEvent::GestureTap:
     case WebInputEvent::GestureTapCancel:
-    case WebInputEvent::GestureDoubleTap:
       if (!waiting_for_tap_end_)
         error_msg->append("Missing GestureTapDown event\n");
       waiting_for_tap_end_ = false;
       break;
+    case WebInputEvent::GestureDoubleTap:
+      waiting_for_tap_end_ = false;
+      break;
     default:
       break;
   }