aura-x11: Add support for xmodmap'ed pointer buttons.

ui/aura/desktop_host_linux.cc

Index: ui/aura/desktop_host_linux.cc
diff --git a/ui/aura/desktop_host_linux.cc b/ui/aura/desktop_host_linux.cc
index 6025de5a7e1bc84eb8ed114a8fabe0d5e7457be6..6b7d37bed678d952a487659f78310ea72ead3df3 100644
--- a/ui/aura/desktop_host_linux.cc
+++ b/ui/aura/desktop_host_linux.cc
@@ -39,6 +39,7 @@ void CheckXEventForConsistency(XEvent* xevent) {
   static bool expect_master_event = false;
   static XIDeviceEvent slave_event;
   static gfx::Point slave_location;
+  static int slave_button;
 
   // Note: If an event comes from a slave pointer device, then it will be
   // followed by the same event, but reported from its master pointer device.
@@ -62,6 +63,7 @@ void CheckXEventForConsistency(XEvent* xevent) {
   if (xievent->sourceid == xievent->deviceid) {
     slave_event = *xievent;
     slave_location = ui::EventLocationFromNative(xevent);
+    slave_button = ui::EventButtonFromNative(xevent);
     expect_master_event = true;
   } else if (was_expecting_master_event) {
     CHECK_EQ(slave_location.x(), ui::EventLocationFromNative(xevent).x());
@@ -69,7 +71,7 @@ void CheckXEventForConsistency(XEvent* xevent) {
 
     CHECK_EQ(slave_event.type, xievent->type);
     CHECK_EQ(slave_event.evtype, xievent->evtype);
-    CHECK_EQ(slave_event.detail, xievent->detail);
+    CHECK_EQ(slave_button, ui::EventButtonFromNative(xevent));
     CHECK_EQ(slave_event.flags, xievent->flags);
     CHECK_EQ(slave_event.buttons.mask_len, xievent->buttons.mask_len);
     CHECK_EQ(slave_event.valuators.mask_len, xievent->valuators.mask_len);