Make Interaction Media Features MQ dynamic on Windows.

content/browser/renderer_host/render_view_host_impl.cc

Index: content/browser/renderer_host/render_view_host_impl.cc
diff --git a/content/browser/renderer_host/render_view_host_impl.cc b/content/browser/renderer_host/render_view_host_impl.cc
index 9e49fb99ec29ec9754a1a5bad63ef3d57bb2bddf..dad9b867ad69cdc4545c970732c1f225d60e53b3 100644
--- a/content/browser/renderer_host/render_view_host_impl.cc
+++ b/content/browser/renderer_host/render_view_host_impl.cc
@@ -234,6 +234,8 @@ RenderViewHostImpl::RenderViewHostImpl(
 
   close_timeout_.reset(new TimeoutMonitor(base::Bind(
       &RenderViewHostImpl::ClosePageTimeout, weak_factory_.GetWeakPtr())));
+
+  input_device_change_observer_.reset(new InputDeviceChangeObserver(this));
 }
 
 RenderViewHostImpl::~RenderViewHostImpl() {
@@ -244,7 +246,6 @@ RenderViewHostImpl::~RenderViewHostImpl() {
                    base::Unretained(ResourceDispatcherHostImpl::Get()),
                    GetProcess()->GetID(), GetRoutingID()));
   }
-
   delegate_->RenderViewDeleted(this);
   GetProcess()->RemoveObserver(this);
 }
@@ -905,6 +906,15 @@ void RenderViewHostImpl::OnWebkitPreferencesChanged() {
   updating_web_preferences_ = false;
 }
 
+bool RenderViewHostImpl::InputDeviceFeaturesChanged() {

[jam, 2017/04/10 15:01:06]

why not do this in InputDeviceChangeObserver, then you can avoid exposing this
one-off method on RVH? RVH already has a public GetWebKitPreferences.

+  WebPreferences prefs = GetWebkitPreferences();
+  int available_pointer_types, available_hover_types;
+  std::tie(available_pointer_types, available_hover_types) =
+      ui::GetAvailablePointerAndHoverTypes();
+  return prefs.available_pointer_types != available_pointer_types ||
+         prefs.available_hover_types != available_hover_types;
+}
+
 void RenderViewHostImpl::DisableScrollbarsForThreshold(const gfx::Size& size) {
   Send(new ViewMsg_DisableScrollbarsForSmallWindows(GetRoutingID(), size));
 }