aura-x11: Avoid calling XISelectEvents on the root-window multiple times.

ui/aura/root_window_host_linux.cc

Index: ui/aura/root_window_host_linux.cc
diff --git a/ui/aura/root_window_host_linux.cc b/ui/aura/root_window_host_linux.cc
index f2d00323ddbc9519c443ac74fd7f8525ea1b0089..d02a41ab58007476146dedf6c2e9ab1e505e61f5 100644
--- a/ui/aura/root_window_host_linux.cc
+++ b/ui/aura/root_window_host_linux.cc
@@ -93,7 +93,17 @@ void SelectEventsForRootWindow() {
                  StructureNotifyMask | attr.your_event_mask);
   }
 
-  XIEventMask evmask;
+  if (!base::MessagePumpForUI::HasXInput2())
+    return;
+
+  int num_masks = -1;
+  XIEventMask* current_mask = XIGetSelectedEvents(display, root_window,
+      &num_masks);
+  if (current_mask) {
+    XFree(current_mask);
+    return;
+  }
+
   unsigned char mask[XIMaskLen(XI_LASTEVENT)] = {};
   memset(mask, 0, sizeof(mask));
 
@@ -107,6 +117,8 @@ void SelectEventsForRootWindow() {
   XISetMask(mask, XI_TouchUpdate);
   XISetMask(mask, XI_TouchEnd);
 #endif
+
+  XIEventMask evmask;
   evmask.deviceid = XIAllDevices;
   evmask.mask_len = sizeof(mask);
   evmask.mask = mask;