Correct behaviour of touch wrt mouse capture.

base/win/win_util.cc

Index: base/win/win_util.cc
diff --git a/base/win/win_util.cc b/base/win/win_util.cc
index 55a4c3c334f071a0cfe279559facbea4852900d2..1fc34e27800b4f01b35edee8acb0bad64ecd826b 100644
--- a/base/win/win_util.cc
+++ b/base/win/win_util.cc
@@ -23,6 +23,9 @@
 
 namespace {
 
+// From MSDN.
+#define MOUSEEVENTF_FROMTOUCH 0xFF515700
+
 // TODO(gab): These definitions are temporary and should be removed once the
 // win8 SDK defines them.
 DEFINE_PROPERTYKEY(PKEY_AppUserModel_DualMode, 0x9F4C2855, 0x9F79,
@@ -110,6 +113,15 @@ bool IsAltPressed() {
   return (::GetKeyState(VK_MENU) & 0x8000) == 0x8000;
 }
 
+// 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;
+}
+
 bool UserAccountControlIsEnabled() {
   // This can be slow if Windows ends up going to disk.  Should watch this key
   // for changes and only read it once, preferably on the file thread.