Introduce painted-device-scale-factor and use it when --enable-use-zoom-for-dsf is specified.

content/renderer/gpu/render_widget_compositor.cc

Index: content/renderer/gpu/render_widget_compositor.cc
diff --git a/content/renderer/gpu/render_widget_compositor.cc b/content/renderer/gpu/render_widget_compositor.cc
index c684a3726600f88c53f1746928f0cb2334ecfa1e..2577f9e42ae4dad86b7a06493c3a8a75be225a13 100644
--- a/content/renderer/gpu/render_widget_compositor.cc
+++ b/content/renderer/gpu/render_widget_compositor.cc
@@ -605,12 +605,6 @@ void RenderWidgetCompositor::detachCompositorAnimationTimeline(
 }
 
 void RenderWidgetCompositor::setViewportSize(
-    const WebSize&,
-    const WebSize& device_viewport_size) {
-  layer_tree_host_->SetViewportSize(device_viewport_size);
-}
-
-void RenderWidgetCompositor::setViewportSize(
     const WebSize& device_viewport_size) {
   layer_tree_host_->SetViewportSize(device_viewport_size);
 }
@@ -621,7 +615,10 @@ WebFloatPoint RenderWidgetCompositor::adjustEventPointForPinchZoom(
 }
 
 void RenderWidgetCompositor::setDeviceScaleFactor(float device_scale) {
-  layer_tree_host_->SetDeviceScaleFactor(device_scale);
+  if (IsUseZoomForDSFEnabled())
+    layer_tree_host_->SetPaintedDeviceScaleFactor(device_scale);
+  else
+    layer_tree_host_->SetDeviceScaleFactor(device_scale);
 }
 
 void RenderWidgetCompositor::setBackgroundColor(blink::WebColor color) {