Remove WebLayerTreeView::deviceViewportSize(), nothing uses it.

Review URL: https://codereview.chromium.org/1314543009

git-svn-id: svn://svn.chromium.org/blink/trunk@201769 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/public/platform/WebLayerTreeView.h

@@ -63,8 +63,6 @@ public:
     // View properties ---------------------------------------------------
 
     virtual void setViewportSize(const WebSize& deviceViewportSize) { }
-    // Gives the viewport size in physical device pixels.
-    virtual WebSize deviceViewportSize() const { return WebSize(); }
 
     virtual void setDeviceScaleFactor(float) { }
     virtual float deviceScaleFactor() const { return 0; }