[Android] Enable input event stream validation

content/common/input/gesture_event_stream_validator.cc

 // Copyright 2014 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/common/input/gesture_event_stream_validator.h"
 
 #include "base/logging.h"
 #include "third_party/WebKit/public/web/WebInputEvent.h"
 
 using blink::WebInputEvent;
 
 namespace content {
 
 GestureEventStreamValidator::GestureEventStreamValidator()
     : scrolling_(false), pinching_(false), waiting_for_tap_end_(false) {
 }
 
 GestureEventStreamValidator::~GestureEventStreamValidator() {
 }
 
 bool GestureEventStreamValidator::Validate(const blink::WebGestureEvent& event,
                                            std::string* error_msg) {
   DCHECK(error_msg);
   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:
     case WebInputEvent::GestureScrollUpdateWithoutPropagation:
       if (!scrolling_)
         error_msg->append("Scroll update outside of scroll\n");
       break;
     case WebInputEvent::GestureScrollEnd:
     case WebInputEvent::GestureFlingStart:
       if (!scrolling_)
         error_msg->append("Scroll end outside of scroll\n");
       if (pinching_)
         error_msg->append("Ending scroll while pinching\n");
       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;
     case WebInputEvent::GestureTapDown:
       if (waiting_for_tap_end_)
         error_msg->append("Missing tap end event\n");
       waiting_for_tap_end_ = true;
       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;
   }
   return error_msg->empty();
 }
 
 }  // namespace content