Correct behaviour of touch wrt mouse capture.

ui/base/win/events_win.cc

Index: ui/base/win/events_win.cc
diff --git a/ui/base/win/events_win.cc b/ui/base/win/events_win.cc
index 3afddc293daf1d04851a62058b83f96778feb3df..212002597b22b0f23bdff88b2e93df532f84414a 100644
--- a/ui/base/win/events_win.cc
+++ b/ui/base/win/events_win.cc
@@ -14,6 +14,9 @@
 
 namespace {
 
+// From MSDN.
+#define MOUSEEVENTF_FROMTOUCH 0xFF515700
+
 // Get the native mouse key state from the native event message type.
 int GetNativeMouseKey(const base::NativeEvent& native_event) {
   switch (native_event.message) {
@@ -312,4 +315,13 @@ int GetModifiersFromACCEL(const ACCEL& accel) {
   return modifiers;
 }
 
+// Windows emulates mouse messages for touch events.
+bool IsMouseEventFromTouch(UINT message) {
+  return (message == WM_MOUSEMOVE ||
+      message == WM_LBUTTONDOWN || message == WM_LBUTTONUP ||
+      message == WM_RBUTTONDOWN || message == WM_RBUTTONUP) &&
+      (GetMessageExtraInfo() & MOUSEEVENTF_FROMTOUCH) ==
+      MOUSEEVENTF_FROMTOUCH;
+}
+
 }  // namespace ui