Identity the mouse pointer type from low-level events for Windows

ui/events/win/events_win.cc

Index: ui/events/win/events_win.cc
diff --git a/ui/events/win/events_win.cc b/ui/events/win/events_win.cc
index cd8dbc72c99e12385a6f6bfe9df9a79b865bdd8d..315d99349da5c6e1b1625b24058b0eb516b63ad4 100644
--- a/ui/events/win/events_win.cc
+++ b/ui/events/win/events_win.cc
@@ -19,9 +19,12 @@ namespace ui {
 namespace {
 
 // From MSDN: "Mouse" events are flagged with 0xFF515700 if they come
-// from a touch or stylus device.  In Vista or later, they are also flagged
-// with 0x80 if they come from touch.
-#define MOUSEEVENTF_FROMTOUCH (0xFF515700 | 0x80)
+// from a touch or stylus device.  In Vista or later, the eighth bit,
+// masked by 0x80, is used to differentiate touch input from pen input
+// (0 = pen, 1 = touch).
+#define MOUSEEVENTF_FROMTOUCHPEN 0xFF515700
+#define MOUSEEVENTF_FROMTOUCH (MOUSEEVENTF_FROMTOUCHPEN | 0x80)
+#define SIGNATURE_MASK 0xFFFFFF00
 
 // Get the native mouse key state from the native event message type.
 int GetNativeMouseKey(const base::NativeEvent& native_event) {
@@ -292,7 +295,12 @@ int GetChangedMouseButtonFlagsFromNative(
 
 PointerDetails GetMousePointerDetailsFromNative(
     const base::NativeEvent& native_event) {
-  return PointerDetails(EventPointerType::POINTER_TYPE_MOUSE);
+  // We should filter out all the mouse events Synthesized from touch events.
+  // TODO(lanwei): Will set the pointer ID, see https://crbug.com/616771.
+  if ((GetMessageExtraInfo() & SIGNATURE_MASK) != MOUSEEVENTF_FROMTOUCHPEN)
+    return PointerDetails(EventPointerType::POINTER_TYPE_MOUSE);
+
+  return PointerDetails(EventPointerType::POINTER_TYPE_PEN);
 }
 
 gfx::Vector2d GetMouseWheelOffset(const base::NativeEvent& native_event) {