Adds DevTools commands for forced viewport override.

third_party/WebKit/Source/web/WebViewImpl.h

Index: third_party/WebKit/Source/web/WebViewImpl.h
diff --git a/third_party/WebKit/Source/web/WebViewImpl.h b/third_party/WebKit/Source/web/WebViewImpl.h
index b324f6cbf587cf5753c8568c4c7c340cb938b8d2..46ac8983fcbaa927145d4e364412bc2341a08973 100644
--- a/third_party/WebKit/Source/web/WebViewImpl.h
+++ b/third_party/WebKit/Source/web/WebViewImpl.h
@@ -302,7 +302,12 @@ public:
     void setBackgroundColorOverride(WebColor);
     void setZoomFactorOverride(float);
     void setCompositorDeviceScaleFactorOverride(float);
-    void setRootLayerTransform(const WebSize& offset, float scale);
+    void setRootLayerTransform(const TransformationMatrix&);
+    TransformationMatrix getRootLayerTransformForTesting() const;
+
+    // Returns the original device scale factor when overridden by DevTools, or
+    // deviceScaleFactor() otherwise.
+    float compositorDeviceScaleFactor() const;
 
     Color baseBackgroundColor() const { return m_baseBackgroundColor; }
 
@@ -384,6 +389,7 @@ public:
 
     void didChangeContentsSize();
     void pageScaleFactorChanged();
+    void mainFrameScrollOffsetChanged();
 
     // Returns true if popup menus should be rendered by the browser, false if
     // they should be rendered by WebKit (which is the default).
@@ -687,8 +693,7 @@ private:
     bool m_ignoreInputEvents;
 
     float m_compositorDeviceScaleFactorOverride;
-    WebSize m_rootLayerOffset;
-    float m_rootLayerScale;
+    TransformationMatrix m_rootLayerTransform;
 
     // Webkit expects keyPress events to be suppressed if the associated keyDown
     // event was handled. Safari implements this behavior by peeking out the