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

third_party/WebKit/public/web/WebWidgetClient.h

Index: third_party/WebKit/public/web/WebWidgetClient.h
diff --git a/third_party/WebKit/public/web/WebWidgetClient.h b/third_party/WebKit/public/web/WebWidgetClient.h
index 8a937cfa5638a2d493d67d4c892a607bc291ef30..41fe6692ea5aac06cdf84e4e3614cece960bdede 100644
--- a/third_party/WebKit/public/web/WebWidgetClient.h
+++ b/third_party/WebKit/public/web/WebWidgetClient.h
@@ -117,9 +117,6 @@ public:
     // displayed.
     virtual WebScreenInfo screenInfo() { return WebScreenInfo(); }
 
-    // Called to get the scale factor of the display.
-    virtual float deviceScaleFactor() { return 1; }
-
     // When this method gets called, WebWidgetClient implementation should
     // reset the input method by cancelling any ongoing composition.
     virtual void resetInputMethod() { }