Make Interaction Media Features MQ dynamic on Windows.

content/browser/renderer_host/input/input_device_change_observer.cc

+// Copyright (c) 2017 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/input/input_device_change_observer.h"
+
+#if defined(OS_WIN)
+#include "ui/events/devices/input_device_observer_win.h"
+#endif
+
+namespace content {
+
+InputDeviceChangeObserver::InputDeviceChangeObserver(RenderViewHost* rvh) {
+  render_view_host_ = rvh;
+#if defined(OS_WIN)
+  ui::InputDeviceObserverWin::GetInstance()->AddObserver(this);
+#endif
+}
+
+InputDeviceChangeObserver::~InputDeviceChangeObserver() {
+#if defined(OS_WIN)
+  ui::InputDeviceObserverWin::GetInstance()->RemoveObserver(this);
+#endif
+  render_view_host_ = nullptr;
+}
+
+void InputDeviceChangeObserver::OnTouchscreenDeviceConfigurationChanged() {
+  notifyRenderViewHost();
+}
+
+void InputDeviceChangeObserver::OnKeyboardDeviceConfigurationChanged() {
+  notifyRenderViewHost();
+}
+
+void InputDeviceChangeObserver::OnMouseDeviceConfigurationChanged() {
+  notifyRenderViewHost();
+}
+
+void InputDeviceChangeObserver::OnTouchpadDeviceConfigurationChanged() {
+  notifyRenderViewHost();
+}
+
+void InputDeviceChangeObserver::notifyRenderViewHost() {
+  if (render_view_host_->InputDeviceFeaturesChanged())

[Rick Byers, 2017/04/05 18:45:50]

In case there turns out to be some pathological case where this gets called a
lot, please add a TRACE here.  Eg. TRACE_EVENT("input",
"InputDeviceChangeObserver::notifyRendererViewHost").  Should be unlikely
though.

+    render_view_host_->OnWebkitPreferencesChanged();
+}
+
+}  // namespace content