[UseZoomForDSF] Guest view support

content/browser/frame_host/render_widget_host_view_guest.cc

Index: content/browser/frame_host/render_widget_host_view_guest.cc
diff --git a/content/browser/frame_host/render_widget_host_view_guest.cc b/content/browser/frame_host/render_widget_host_view_guest.cc
index 6d4a1811c5bc9eae2ed516d37e990a25d42bc905..99a235dc83ae84f592a41d3cf5bf2763342c6254 100644
--- a/content/browser/frame_host/render_widget_host_view_guest.cc
+++ b/content/browser/frame_host/render_widget_host_view_guest.cc
@@ -62,6 +62,8 @@ RenderWidgetHostViewGuest::RenderWidgetHostViewGuest(
       // |guest| is NULL during test.
       guest_(guest ? guest->AsWeakPtr() : base::WeakPtr<BrowserPluginGuest>()),
       platform_view_(platform_view) {
+  // Inputs for guest view are already scaled.
+  host_->set_scale_input_to_viewport(false);

[no sievers, 2016/01/26 19:42:35]

Is it possible for this |host_| to host an interstitial page or other kind of
view?

I'm wondering if it's better for the RWHV to query the RWHV for this flag. wdyt?

 }
 
 RenderWidgetHostViewGuest::~RenderWidgetHostViewGuest() {