Mark touchcancel events as uncancelable

content/common/input/web_touch_event_traits.h

+// 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.
+
+#ifndef CONTENT_COMMON_INPUT_WEB_TOUCH_EVENT_TRAITS_H_
+#define CONTENT_COMMON_INPUT_WEB_TOUCH_EVENT_TRAITS_H_
+
+#include "base/basictypes.h"
+#include "content/common/input/scoped_web_input_event.h"
+#include "third_party/WebKit/public/web/WebInputEvent.h"
+
+namespace content {
+
+// Utility class for performing operations on and with WebTouchEvents.
+class CONTENT_EXPORT WebTouchEventTraits {
+ public:
+
+  // Returns whether all touches in the event have the specified state.
+  static bool AllTouchPointsHaveState(
+      const blink::WebTouchEvent& event,
+      blink::WebTouchPoint::State state);
+
+  // Returns whether this event represents a transition from no active
+  // touches to some active touches (the start of a new "touch sequence").
+  static bool IsTouchSequenceStart(const blink::WebTouchEvent& event);
+
+  // Sets the type of |event| to |type|, resetting any other type-specific
+  // properties and updating the timestamp and touches as requested.
+  // This is particularly useful, for example, in sending a touchcancel
+  // for all active touches.
+  enum ResetTouchesMode {
+    // Don't modify the Touches at all.
+    IGNORE_TOUCHES_STATE,
+    // Reset the state of every active Touch to match the event type.
+    RESET_TOUCHES_STATE
+  };
+  static void ResetType(blink::WebTouchEvent* event,

[jdduke (slow), 2014/04/23 21:55:47]

I'd much prefer two methods here, |ResetType| and |ResetTypeAndTouchStates|, one
augmenting the other internally.

Normally "out" type parameters are last in the ordering.  Any reason you put it
first?

[Rick Byers, 2014/04/23 23:15:35]

Done.
I was thinking of it as in/out, but it looks like the style guide prefers those
to be last as well (although it's a little vague).  I've moved it last.

+                        blink::WebInputEvent::Type type,
+                        double timestamp_sec,
+                        ResetTouchesMode);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_COMMON_INPUT_WEB_TOUCH_EVENT_TRAITS_H_