Track whether a scroll sequence has been partially prevented

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 "base/strings/stringprintf.h"
+#include "content/common/input/web_input_event_traits.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();
+  if (!WebInputEvent::isGestureEventType(event.type)) {
+    error_msg->append(base::StringPrintf(
+        "Invalid gesture type: %s", WebInputEventTraits::GetName(event.type)));
+  }
   switch (event.type) {
     case WebInputEvent::GestureScrollBegin:
       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:
@@ skipping 42 matching lines @@
       // not require a preceding TapDown.
       waiting_for_tap_end_ = false;
       break;
     default:
       break;
   }
   return error_msg->empty();
 }
 
 }  // namespace content