Refactor fixed layout mode

Source/web/WebViewImpl.h

Index: Source/web/WebViewImpl.h
diff --git a/Source/web/WebViewImpl.h b/Source/web/WebViewImpl.h
index 3112cc6106dfd3b3291b29336abcc29ad4a718f3..a2e9aff6fda808158856d8f14bb463d31045ee9c 100644
--- a/Source/web/WebViewImpl.h
+++ b/Source/web/WebViewImpl.h
@@ -240,10 +240,15 @@ public:
 
     virtual float deviceScaleFactor() const;
     virtual void setDeviceScaleFactor(float);
-    virtual bool isFixedLayoutModeEnabled() const;
-    virtual void enableFixedLayoutMode(bool enable);
-    virtual WebSize fixedLayoutSize() const;
+
     virtual void setFixedLayoutSize(const WebSize&);
+
+    // DEPRECATED: Will be removed soon.
+    // See https://codereview.chromium.org/23819019/
+    virtual bool isFixedLayoutModeEnabled() const { return true; }
+    virtual void enableFixedLayoutMode(bool) { }
+    virtual WebSize fixedLayoutSize() const { return WebSize(); }
+
     virtual void enableAutoResizeMode(
         const WebSize& minSize,
         const WebSize& maxSize);
@@ -446,7 +451,8 @@ public:
         return m_maxAutoSize;
     }
 
-    void updatePageDefinedPageScaleConstraints(const WebCore::ViewportDescription&);
+    void updateMainFrameLayoutSize();
+    void updatePageDefinedViewportConstraints(const WebCore::ViewportDescription&);
 
     // Start a system drag and drop operation.
     void startDragging(