Make Interaction Media Features MQ dynamic on Windows.

content/browser/renderer_host/render_view_host_impl.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_view_host_impl.h"
 
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 216 matching lines @@
   if (ResourceDispatcherHostImpl::Get()) {
     BrowserThread::PostTask(
         BrowserThread::IO, FROM_HERE,
         base::Bind(&ResourceDispatcherHostImpl::OnRenderViewHostCreated,
                    base::Unretained(ResourceDispatcherHostImpl::Get()),
                    GetProcess()->GetID(), GetRoutingID()));
   }
 
   close_timeout_.reset(new TimeoutMonitor(base::Bind(
       &RenderViewHostImpl::ClosePageTimeout, weak_factory_.GetWeakPtr())));
+
+  input_device_change_observer_.reset(new InputDeviceChangeObserver(this));
 }
 
 RenderViewHostImpl::~RenderViewHostImpl() {
   if (ResourceDispatcherHostImpl::Get()) {
     BrowserThread::PostTask(
         BrowserThread::IO, FROM_HERE,
         base::Bind(&ResourceDispatcherHostImpl::OnRenderViewHostDeleted,
                    base::Unretained(ResourceDispatcherHostImpl::Get()),
                    GetProcess()->GetID(), GetRoutingID()));
   }
-
   delegate_->RenderViewDeleted(this);
   GetProcess()->RemoveObserver(this);
 }
 
 RenderViewHostDelegate* RenderViewHostImpl::GetDelegate() const {
   return delegate_;
 }
 
 SiteInstanceImpl* RenderViewHostImpl::GetSiteInstance() const {
   return instance_.get();
@@ skipping 640 matching lines @@
   // This is defensive code to avoid infinite loops due to code run inside
   // UpdateWebkitPreferences() accidentally updating more preferences and thus
   // calling back into this code. See crbug.com/398751 for one past example.
   if (updating_web_preferences_)
     return;
   updating_web_preferences_ = true;
   UpdateWebkitPreferences(ComputeWebkitPrefs());
   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));
 }
 
 void RenderViewHostImpl::EnablePreferredSizeMode() {
   Send(new ViewMsg_EnablePreferredSizeChangedMode(GetRoutingID()));
 }
 
 void RenderViewHostImpl::EnableAutoResize(const gfx::Size& min_size,
                                           const gfx::Size& max_size) {
@@ skipping 43 matching lines @@
 }
 
 void RenderViewHostImpl::ClosePageTimeout() {
   if (delegate_->ShouldIgnoreUnresponsiveRenderer())
     return;
 
   ClosePageIgnoringUnloadEvents();
 }
 
 }  // namespace content