Add support for new scroll valuators coming from CMT

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 a2c4a731a11e4153a0c838c901de236f53c38814..25ef06e266f0da0928480f7cecf7268c693c170e 100644
--- a/ui/aura/root_window_host_linux.cc
+++ b/ui/aura/root_window_host_linux.cc
@@ -19,6 +19,7 @@
 #include "ui/aura/root_window.h"
 #include "ui/base/keycodes/keyboard_codes.h"
 #include "ui/base/touch/touch_factory.h"
+#include "ui/base/x/scroll_factory.h"
 #include "ui/base/x/x11_util.h"
 #include "ui/gfx/compositor/layer.h"
 
@@ -197,7 +198,9 @@ int CoalescePendingXIMotionEvents(const XEvent* xev, XEvent* last_event) {
     }
 
     if (next_event.type == GenericEvent &&
-        next_event.xgeneric.evtype == XI_Motion) {
+        next_event.xgeneric.evtype == XI_Motion &&
+        !ui::ScrollFactory::GetInstance()->GetScrollOffsets(
+            next_event, NULL, NULL)) {
       XIDeviceEvent* next_xievent =
           static_cast<XIDeviceEvent*>(next_event.xcookie.data);
       // Confirm that the motion event is targeted at the same window
@@ -422,17 +425,20 @@ base::MessagePumpDispatcher::DispatchStatus RootWindowHostLinux::Dispatch(
       if (!factory->ShouldProcessXI2Event(xev))
         break;
 
+      // Update the device list if necessary.
+      if (xev->xgeneric.evtype == XI_HierarchyChanged) {
+        ui::ScrollFactory::GetInstance()->UpdateDeviceList(xdisplay_);
+        factory->UpdateDeviceList(xdisplay_);
+        handled = true;
+        break;
+      }
+
+      ui::EventType type = ui::EventTypeFromNative(xev);
       // If this is a motion event we want to coalesce all pending motion
       // events that are at the top of the queue.
       XEvent last_event;
       int num_coalesced = 0;
-      if (xev->xgeneric.evtype == XI_Motion) {
-        num_coalesced = CoalescePendingXIMotionEvents(xev, &last_event);
-        if (num_coalesced > 0)
-          xev = &last_event;
-      }
 
-      ui::EventType type = ui::EventTypeFromNative(xev);
       switch (type) {
         case ui::ET_TOUCH_PRESSED:
         case ui::ET_TOUCH_RELEASED:
@@ -441,10 +447,16 @@ base::MessagePumpDispatcher::DispatchStatus RootWindowHostLinux::Dispatch(
           handled = root_window_->DispatchTouchEvent(&touchev);
           break;
         }
+        case ui::ET_MOUSE_MOVED:
+        case 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 = CoalescePendingXIMotionEvents(xev, &last_event);
+          if (num_coalesced > 0)
+            xev = &last_event;
+        }
         case ui::ET_MOUSE_PRESSED:
         case ui::ET_MOUSE_RELEASED:
-        case ui::ET_MOUSE_MOVED:
-        case ui::ET_MOUSE_DRAGGED:
         case ui::ET_MOUSEWHEEL:
         case ui::ET_MOUSE_ENTERED:
         case ui::ET_MOUSE_EXITED: {
@@ -452,6 +464,11 @@ base::MessagePumpDispatcher::DispatchStatus RootWindowHostLinux::Dispatch(
           handled = root_window_->DispatchMouseEvent(&mouseev);
           break;
         }
+        case ui::ET_SCROLL: {
+          ScrollEvent scrollev(xev);
+          handled = root_window_->DispatchScrollEvent(&scrollev);
+          break;
+        }
         case ui::ET_UNKNOWN:
           handled = false;
           break;