Use constrained values for shouldDisableDesktopWorkarounds.

Source/web/WebViewImpl.cpp

 /*
  * Copyright (C) 2011, 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 4088 matching lines @@
     const WebMouseEvent& mouseEvent = static_cast<const WebMouseEvent&>(event);
 
     if (page())
         page()->pointerLockController().dispatchLockedMouseEvent(
             PlatformMouseEventBuilder(mainFrameImpl()->frameView(), mouseEvent),
             eventType);
 }
 
 bool WebViewImpl::shouldDisableDesktopWorkarounds()
 {
-    ViewportArguments arguments = mainFrameImpl()->frame()->document()->viewportArguments();
-    return arguments.width == ViewportArguments::ValueDeviceWidth || !arguments.userZoom
-        || (arguments.minZoom == arguments.maxZoom && arguments.minZoom != ViewportArguments::ValueAuto);
+    if (!settings()->viewportEnabled() || !isFixedLayoutModeEnabled())
+        return false;
+
+    // A document is considered adapted to small screen UAs if one of these holds:
+    // 1. The author specified viewport has a constrained width that is equal to
+    //    the initial viewport width.
+    // 2. The author has disabled viewport zoom.
+
+    const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
+
+    return fixedLayoutSize().width == m_size.width
+        || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace WebKit