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

third_party/WebKit/public/web/WebView.h

Index: third_party/WebKit/public/web/WebView.h
diff --git a/third_party/WebKit/public/web/WebView.h b/third_party/WebKit/public/web/WebView.h
index ccd46ce923ab392a5ec3aa6c8e7f44ebcbcfe5de..49a848d50f322a51b5fc58e32a8eceb17afe3e98 100644
--- a/third_party/WebKit/public/web/WebView.h
+++ b/third_party/WebKit/public/web/WebView.h
@@ -291,8 +291,14 @@ public:
     virtual float deviceScaleFactor() const = 0;
 
     // Sets the ratio as computed by computePageScaleConstraints.
+    // TODO(oshima): Remove this once the device scale factor implementation is fully
+    // migrated to use zooming mechanism.
     virtual void setDeviceScaleFactor(float) = 0;
 
+    // Sets the additional zoom factor used for device scale factor. This is used
+    // to scale the content by the device scale factor, without affecting zoom level.
+    virtual void setZoomFactorForDeviceScaleFactor(float) = 0;
+
     // Set and reset the device color profile.
     virtual void setDeviceColorProfile(const WebVector<char>&) = 0;
     virtual void resetDeviceColorProfile() = 0;