Fix a crash when views::HWNDMessageHandler::HandleTouchMessage

ui/views/win/hwnd_message_handler.cc

Index: ui/views/win/hwnd_message_handler.cc
diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index cb34bbe7999d9a4412b27e04a1656cc2265a5d2d..4aae47eecff403973ddc3591f7d83b4adfa0f497 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -2350,6 +2350,11 @@ void HWNDMessageHandler::PrepareTouchEventList(TOUCHINPUT input[],
 
     ScreenToClient(hwnd(), &point);
 
+    // We set a check to assert that we do not receive any touch events from
+    // user's palm.
+    bool touch_event_from_palm = (input[i].dwFlags & TOUCHEVENTF_PALM) != 0;
+    CHECK(!touch_event_from_palm) << "There are touch events from user's palm";

[sadrul, 2015/05/19 23:38:12]

I don't think we should crash here? Why not just ignore this event?

[ananta, 2015/05/19 23:40:18]

Wanted to check if the missing touch downs are because of us receiving a touch
palm event. We register for palms as well. If this CHECK fires then we can treat
palms as downs.

[sadrul, 2015/05/19 23:51:13]

Should we keep the old CHECKs too then? If the palms are the downs we are
missing, then the we would trip this CHECK, and not the the one in 2399. But if
there are some other reason the downs are missing, we will miss that without the
CHECK below, right?

+
     // TOUCHEVENTF_DOWN cannot be combined with TOUCHEVENTF_MOVE or
     // TOUCHEVENTF_UP, but TOUCHEVENTF_MOVE and TOUCHEVENTF_UP can be combined
     // in one input.
@@ -2392,12 +2397,6 @@ void HWNDMessageHandler::GenerateTouchEvent(DWORD input_dwID,
   // touchevent time.
   base::TimeDelta now = ui::EventTimeForNow();
 
-  // We set a check to assert that we do not have missing touch presses in
-  // every message.
-  bool has_missing_touch_press = touch_event_type != ui::ET_TOUCH_PRESSED &&
-      touch_point.in_touch_list == InTouchList::NotPresent;
-  CHECK(!has_missing_touch_press) << "There are missing touch presses";
-
   ui::TouchEvent event(touch_event_type, point_location, touch_id, now);
   event.set_flags(flags);
   event.latency()->AddLatencyNumberWithTimestamp(