overscroll-aura: Discard synthetic mouse-move events during a trackpad overscroll.

content/browser/renderer_host/render_widget_host_view_aura.cc

Index: content/browser/renderer_host/render_widget_host_view_aura.cc
diff --git a/content/browser/renderer_host/render_widget_host_view_aura.cc b/content/browser/renderer_host/render_widget_host_view_aura.cc
index 9af6457c37416647d7b5d03bbf10f2608d92d12a..c8da65b870907695b8dc121605505b16ec514533 100644
--- a/content/browser/renderer_host/render_widget_host_view_aura.cc
+++ b/content/browser/renderer_host/render_widget_host_view_aura.cc
@@ -13,6 +13,7 @@
 #include "base/string_number_conversions.h"
 #include "content/browser/renderer_host/backing_store_aura.h"
 #include "content/browser/renderer_host/dip_util.h"
+#include "content/browser/renderer_host/overscroll_controller.h"
 #include "content/browser/renderer_host/render_view_host_delegate.h"
 #include "content/browser/renderer_host/render_widget_host_impl.h"
 #include "content/browser/renderer_host/ui_events_helper.h"
@@ -1569,6 +1570,20 @@ ui::EventResult RenderWidgetHostViewAura::OnMouseEvent(ui::MouseEvent* event) {
     return ui::ER_UNHANDLED;
   }
 
+  // As the overscroll is handled during scroll events from the trackpad, the
+  // RWHVA window is transformed by the overscroll controller. This transform
+  // triggers a synthetic mouse-move event to be generated (by the aura
+  // RootWindow). But this event interferes with the overscroll gesture. So,
+  // ignore such synthetic mouse-move events if an overscroll gesture is in
+  // progress.
+  if (host_->overscroll_controller() &&
+      host_->overscroll_controller()->overscroll_mode() != OVERSCROLL_NONE &&
+      event->flags() & ui::EF_IS_SYNTHESIZED &&
+      (event->type() == ui::ET_MOUSE_ENTERED ||
+       event->type() == ui::ET_MOUSE_MOVED)) {
+    return ui::ER_CONSUMED;
+  }
+
   if (event->type() == ui::ET_MOUSEWHEEL) {
     WebKit::WebMouseWheelEvent mouse_wheel_event =
         MakeWebMouseWheelEvent(static_cast<ui::MouseWheelEvent*>(event));