Add WebPointerProperties type.

public/web/WebInputEvent.h

Index: public/web/WebInputEvent.h
diff --git a/public/web/WebInputEvent.h b/public/web/WebInputEvent.h
index b5d0a8bc6052b1f56fabe2537e52a02a86eb92b8..5093259a41f79fa3b9f48d25b5154db11cae3fda 100644
--- a/public/web/WebInputEvent.h
+++ b/public/web/WebInputEvent.h
@@ -34,6 +34,8 @@
 #include "../platform/WebCommon.h"
 #include "../platform/WebGestureDevice.h"
 #include "../platform/WebRect.h"
+#include "WebMouseProperties.h"
+#include "WebPointerProperties.h"
 #include "WebTouchPoint.h"
 
 #include <string.h>
@@ -300,16 +302,8 @@ public:
 
 // WebMouseEvent --------------------------------------------------------------
 
-class WebMouseEvent : public WebInputEvent {
+class WebMouseEvent : public WebInputEvent, public WebMouseProperties {
 public:
-    enum Button {
-        ButtonNone = -1,
-        ButtonLeft,
-        ButtonMiddle,
-        ButtonRight
-    };
-
-    Button button;
     int x;
     int y;
     int windowX;
@@ -322,7 +316,7 @@ public:
 
     WebMouseEvent()
         : WebInputEvent(sizeof(WebMouseEvent))
-        , button(ButtonNone)
+        , WebMouseProperties()
         , x(0)
         , y(0)
         , windowX(0)
@@ -338,7 +332,7 @@ public:
 protected:
     explicit WebMouseEvent(unsigned sizeParam)
         : WebInputEvent(sizeParam)
-        , button(ButtonNone)
+        , WebMouseProperties()
         , x(0)
         , y(0)
         , windowX(0)
@@ -425,6 +419,17 @@ public:
     }
 };
 
+// WebPointerEvent ------------------------------------------------------------
+
+class WebPointerEvent : public WebMouseEvent, public WebPointerProperties {

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

Let's hold off adding WebPointerEvent until we have a concrete use for it.  I
suspect we'll find it simpler/easier to rename WebMouseEvent to WebPointerEvent
- we probably don't need both at any given time (once the blink and chromium
repositories have merged at least).

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

Done.

+public:
+    WebPointerEvent()
+        : WebMouseEvent(sizeof(WebPointerEvent))
+        , WebPointerProperties()
+    {
+    }
+};
+
 // WebGestureEvent --------------------------------------------------------------
 
 class WebGestureEvent : public WebInputEvent {
@@ -522,6 +527,7 @@ public:
 
 // WebTouchEvent --------------------------------------------------------------
 
+// TODO(e_hakkinen): Replace with WebPointerEvent.
 class WebTouchEvent : public WebInputEvent {
 public:
     // Maximum number of simultaneous touches supported on