Add WebPointerProperties type.

public/web/WebMouseProperties.h

Index: public/web/WebMouseProperties.h
diff --git a/public/web/WebMouseProperties.h b/public/web/WebMouseProperties.h
new file mode 100644
index 0000000000000000000000000000000000000000..9c4c8f3e1a2a24b1bb518a9fbbeba86de70fe1ed
--- /dev/null
+++ b/public/web/WebMouseProperties.h
@@ -0,0 +1,32 @@
+// Copyright (c) 2015 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 WebMouseProperties_h
+#define WebMouseProperties_h
+
+namespace blink {
+
+// TODO(e_hakkinen): Replace WebTouchEvent with WebPointerEvent, remove
+//                   WebTouchEvent and WebTouchPoint and merge this into
+//                   WebMouseEvent.
+class WebMouseProperties {
+public:
+    WebMouseProperties()
+        : button(ButtonNone)
+    {
+    }
+
+    enum Button {
+        ButtonNone = -1,
+        ButtonLeft,
+        ButtonMiddle,
+        ButtonRight
+    };
+
+    Button button;

[Rick Byers, 2015/07/06 17:22:38]

It feels a little odd to have WebMouseProperties in WebTouchPoint.  The only
reason you've separated this out from WebPointerProperties was to avoid bloating
WebMouseEvent with a bunch of normally unused properties, right?

I wouldn't worry about that.  I've done performance tests on the size of
WebTouchEvent and it took a LOT of additional space to have any impact on
performance.  The objects are very short lived and there tends to only be a few
alive at any time, and usually no more than one created per frame.  So the perf
impact of extra fields is low in practice.

So how about we simplify all of this by having only one new class
'WebPointerProperties' - the stuff that we've generalized from mouse events and
touch points along the path to having a unified pointer event.

[USE eero AT chromium.org, 2015/07/07 10:00:55]

Yes.
Done.

+};
+
+} // namespace blink
+
+#endif