Suppress ET_MOUSE_MOVE when the mouse hasn't moved on Windows.

content/browser/renderer_host/render_widget_host_view_aura.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/renderer_host/render_widget_host_view_aura.h"
 
 #include <set>
 #include <utility>
 
 #include "base/auto_reset.h"
@@ skipping 199 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(WinScreenKeyboardObserver);
 };
 #endif  // defined(OS_WIN)
 
 // Callback from embedding the renderer.
 void EmbedCallback(bool result) {
   if (!result)
     DVLOG(1) << "embed failed";
 }
 
+// We need to watch for mouse events outside a Web Popup or its parent
+// and dismiss the popup for certain events.
+class EventFilterForMouseMove : public ui::EventHandler {
+ public:
+  EventFilterForMouseMove() {
+    aura::Env::GetInstance()->AddPreTargetHandler(this);

[sadrul, 2017/01/27 00:22:03]

This should install the event-handler on the RWHVA's |window_|.

... although, why not remember the last location in RWHVA::OnMouseEvent without
installing any pre-target handlers at all?

+  }
+
+  ~EventFilterForMouseMove() override {
+    aura::Env::GetInstance()->RemovePreTargetHandler(this);
+  }
+
+  // Overridden from ui::EventHandler
+  void OnMouseEvent(ui::MouseEvent* event) override {
+    if (event->type() != ui::ET_MOUSE_MOVED)
+      return;
+    if (event->location() == last_location_) {
+      event->SetHandled();
+      return;
+    }
+    last_location_ = event->location();
+  }
+
+ private:
+  gfx::Point last_location_;
+  DISALLOW_COPY_AND_ASSIGN(EventFilterForMouseMove);
+};
+
 }  // namespace
 
 // We need to watch for mouse events outside a Web Popup or its parent
 // and dismiss the popup for certain events.
 class RenderWidgetHostViewAura::EventFilterForPopupExit
     : public ui::EventHandler {
  public:
   explicit EventFilterForPopupExit(RenderWidgetHostViewAura* rwhva)
       : rwhva_(rwhva) {
     DCHECK(rwhva_);
@@ skipping 183 matching lines @@
   selection_controller_client_.reset(
       new TouchSelectionControllerClientAura(this));
   CreateSelectionController();
 
   RenderViewHost* rvh = RenderViewHost::From(host_);
   if (rvh) {
     // TODO(mostynb): actually use prefs.  Landing this as a separate CL
     // first to rebaseline some unreliable layout tests.
     ignore_result(rvh->GetWebkitPreferences());
   }
+
+#if defined(OS_WIN)
+  // Windows will post a WM_MOUSEMOVE after a click event. Other platforms
+  // do not do this so we filter out mouse moves where the position doesn't
+  // change from the last event.
+  event_filter_for_mouse_move_.reset(new EventFilterForMouseMove());
+#endif
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // RenderWidgetHostViewAura, RenderWidgetHostView implementation:
 
 void RenderWidgetHostViewAura::InitAsChild(
     gfx::NativeView parent_view) {
   CreateDelegatedFrameHostClient();
 
   CreateAuraWindow(ui::wm::WINDOW_TYPE_CONTROL);
@@ skipping 1413 matching lines @@
     popup_parent_host_view_->SetPopupChild(nullptr);
   }
   if (popup_child_host_view_) {
     DCHECK(popup_child_host_view_->popup_parent_host_view_ == NULL ||
            popup_child_host_view_->popup_parent_host_view_ == this);
     popup_child_host_view_->popup_parent_host_view_ = NULL;
   }
   event_filter_for_popup_exit_.reset();
 
 #if defined(OS_WIN)
+  event_filter_for_mouse_move_.reset();
+
   // The LegacyRenderWidgetHostHWND window should have been destroyed in
   // RenderWidgetHostViewAura::OnWindowDestroying and the pointer should
   // be set to NULL.
   DCHECK(!legacy_render_widget_host_HWND_);
   if (virtual_keyboard_requested_) {
     DCHECK(keyboard_observer_.get());
     ui::OnScreenKeyboardDisplayManager* osk_display_manager =
         ui::OnScreenKeyboardDisplayManager::GetInstance();
     DCHECK(osk_display_manager);
     osk_display_manager->RemoveObserver(keyboard_observer_.get());
@@ skipping 515 matching lines @@
 
 void RenderWidgetHostViewAura::SetPopupChild(
     RenderWidgetHostViewAura* popup_child_host_view) {
   popup_child_host_view_ = popup_child_host_view;
   event_handler_->SetPopupChild(
       popup_child_host_view,
       popup_child_host_view ? popup_child_host_view->event_handler() : nullptr);
 }
 
 }  // namespace content