Add tablet heuristic detection

base/win/win_util.cc

Index: base/win/win_util.cc
===================================================================
--- base/win/win_util.cc	(revision 156164)
+++ base/win/win_util.cc	(working copy)
@@ -214,6 +214,16 @@
   return g_crash_on_process_detach;
 }
 
+bool IsMachineATablet() {
+  if (base::win::GetVersion() < base::win::VERSION_WIN7)
+    return false;
+  // TODO(ananta): Add keyboard detection logic if it can be made reliable.
+  const int kPenInput = NID_INTEGRATED_PEN | NID_EXTERNAL_PEN;
+  const int kMultiTouch = NID_INTEGRATED_TOUCH | NID_MULTI_INPUT | NID_READY;
+  int sm = GetSystemMetrics(SM_DIGITIZER);
+  return ((sm & kMultiTouch) == kMultiTouch) && ((sm & kPenInput) == 0);
+}
+
 }  // namespace win
 }  // namespace base