linux_aura: Fix tab dragging performance.

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 9b8f3b8a22a4363eea5c6dc5f7149fc6f6843ae7..a85d6ff3b78b9107dd49ac956e9477dd5c50fd97 100644
--- a/ui/aura/root_window_host_linux.cc
+++ b/ui/aura/root_window_host_linux.cc
@@ -31,6 +31,7 @@
 #include "ui/base/ui_base_switches.h"
 #include "ui/base/view_prop.h"
 #include "ui/base/x/valuators.h"
+#include "ui/base/x/x11_util.h"
 #include "ui/compositor/dip_util.h"
 #include "ui/compositor/layer.h"
 #include "ui/gfx/codec/png_codec.h"
@@ -74,91 +75,6 @@ const char* kAtomsToCache[] = {
   return target;
 }
 
-// Coalesce all pending motion events (touch or mouse) that are at the top of
-// the queue, and return the number eliminated, storing the last one in
-// |last_event|.
-int CoalescePendingMotionEvents(const XEvent* xev, XEvent* last_event) {
-  XIDeviceEvent* xievent = static_cast<XIDeviceEvent*>(xev->xcookie.data);
-  int num_coalesed = 0;
-  Display* display = xev->xany.display;
-  int event_type = xev->xgeneric.evtype;
-
-#if defined(USE_XI2_MT)
-  float tracking_id = -1;
-  if (event_type == XI_TouchUpdate) {
-    if (!ui::ValuatorTracker::GetInstance()->ExtractValuator(*xev,
-          ui::ValuatorTracker::VAL_TRACKING_ID, &tracking_id))
-      tracking_id = -1;
-  }
-#endif
-
-  while (XPending(display)) {
-    XEvent next_event;
-    XPeekEvent(display, &next_event);
-
-    // If we can't get the cookie, abort the check.
-    if (!XGetEventData(next_event.xgeneric.display, &next_event.xcookie))
-      return num_coalesed;
-
-    // If this isn't from a valid device, throw the event away, as
-    // that's what the message pump would do. Device events come in pairs
-    // with one from the master and one from the slave so there will
-    // always be at least one pending.
-    if (!ui::TouchFactory::GetInstance()->ShouldProcessXI2Event(&next_event)) {
-      XFreeEventData(display, &next_event.xcookie);
-      XNextEvent(display, &next_event);
-      continue;
-    }
-
-    if (next_event.type == GenericEvent &&
-        next_event.xgeneric.evtype == event_type &&
-        !ui::GetScrollOffsets(&next_event, NULL, NULL)) {
-      XIDeviceEvent* next_xievent =
-          static_cast<XIDeviceEvent*>(next_event.xcookie.data);
-#if defined(USE_XI2_MT)
-      float next_tracking_id = -1;
-      if (event_type == XI_TouchUpdate) {
-        // If this is a touch motion event (as opposed to mouse motion event),
-        // then make sure the events are from the same touch-point.
-        if (!ui::ValuatorTracker::GetInstance()->ExtractValuator(next_event,
-              ui::ValuatorTracker::VAL_TRACKING_ID, &next_tracking_id))
-          next_tracking_id = -1;
-      }
-#endif
-      // Confirm that the motion event is targeted at the same window
-      // and that no buttons or modifiers have changed.
-      if (xievent->event == next_xievent->event &&
-          xievent->child == next_xievent->child &&
-#if defined(USE_XI2_MT)
-          (event_type == XI_Motion || tracking_id == next_tracking_id) &&
-#endif
-          xievent->buttons.mask_len == next_xievent->buttons.mask_len &&
-          (memcmp(xievent->buttons.mask,
-                  next_xievent->buttons.mask,
-                  xievent->buttons.mask_len) == 0) &&
-          xievent->mods.base == next_xievent->mods.base &&
-          xievent->mods.latched == next_xievent->mods.latched &&
-          xievent->mods.locked == next_xievent->mods.locked &&
-          xievent->mods.effective == next_xievent->mods.effective) {
-        XFreeEventData(display, &next_event.xcookie);
-        // Free the previous cookie.
-        if (num_coalesed > 0)
-          XFreeEventData(display, &last_event->xcookie);
-        // Get the event and its cookie data.
-        XNextEvent(display, last_event);
-        XGetEventData(display, &last_event->xcookie);
-        ++num_coalesed;
-        continue;
-      } else {
-        // This isn't an event we want so free its cookie data.
-        XFreeEventData(display, &next_event.xcookie);
-      }
-    }
-    break;
-  }
-  return num_coalesed;
-}
-
 void SelectEventsForRootWindow() {
   Display* display = ui::GetXDisplay();
   ::Window root_window = ui::GetX11RootWindow();
@@ -545,7 +461,7 @@ void RootWindowHostLinux::DispatchXI2Event(const base::NativeEvent& event) {
 
   switch (type) {
     case ui::ET_TOUCH_MOVED:
-      num_coalesced = CoalescePendingMotionEvents(xev, &last_event);
+      num_coalesced = ui::CoalescePendingMotionEvents(xev, &last_event);
       if (num_coalesced > 0)
         xev = &last_event;
       // fallthrough
@@ -584,7 +500,7 @@ void RootWindowHostLinux::DispatchXI2Event(const base::NativeEvent& event) {
       if (type == ui::ET_MOUSE_MOVED || type == ui::ET_MOUSE_DRAGGED) {
         // If this is a motion event, we want to coalesce all pending motion
         // events that are at the top of the queue.
-        num_coalesced = CoalescePendingMotionEvents(xev, &last_event);
+        num_coalesced = ui::CoalescePendingMotionEvents(xev, &last_event);
         if (num_coalesced > 0)
           xev = &last_event;
       } else if (type == ui::ET_MOUSE_PRESSED) {