Update viewport trigger for GPU rasterization

Source/core/dom/ViewportDescription.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2012-2013 Intel Corporation. All rights reserved.
  *
@@ skipping 48 matching lines @@
     };
 
     ViewportDescription(Type type = UserAgentStyleSheet)
         : type(type)
         , zoom(ValueAuto)
         , minZoom(ValueAuto)
         , maxZoom(ValueAuto)
         , userZoom(true)
         , orientation(ValueAuto)
         , deprecatedTargetDensityDPI(ValueAuto)
-        , minimalUI(false)
+        , zoomIsExplicit(false)
+        , minZoomIsExplicit(false)
+        , maxZoomIsExplicit(false)
+        , userZoomIsExplicit(false)
     {
     }
 
     // All arguments are in CSS units.
     PageScaleConstraints resolve(const FloatSize& initialViewportSize, Length legacyFallbackWidth) const;
 
     Length minWidth;
     Length maxWidth;
     Length minHeight;
     Length maxHeight;
     float zoom;
     float minZoom;
     float maxZoom;
     bool userZoom;
     float orientation;
     float deprecatedTargetDensityDPI; // Only used for Android WebView
-    bool minimalUI;
+
+    // Whether the computed value was explicitly specified rather than being
+    // inferred.
+    bool zoomIsExplicit;
+    bool minZoomIsExplicit;
+    bool maxZoomIsExplicit;
+    bool userZoomIsExplicit;
 
     bool operator==(const ViewportDescription& other) const
     {
         // Used for figuring out whether to reset the viewport or not,
         // thus we are not taking type into account.
         return minWidth == other.minWidth
             && maxWidth == other.maxWidth
             && minHeight == other.minHeight
             && maxHeight == other.maxHeight
             && zoom == other.zoom
             && minZoom == other.minZoom
             && maxZoom == other.maxZoom
             && userZoom == other.userZoom
             && orientation == other.orientation
             && deprecatedTargetDensityDPI == other.deprecatedTargetDensityDPI
-            && minimalUI == other.minimalUI;
+            && zoomIsExplicit == other.zoomIsExplicit
+            && minZoomIsExplicit == other.minZoomIsExplicit
+            && maxZoomIsExplicit == other.maxZoomIsExplicit
+            && userZoomIsExplicit == other.userZoomIsExplicit;
     }
 
     bool operator!=(const ViewportDescription& other) const
     {
         return !(*this == other);
     }
 
     bool isLegacyViewportType() const { return type >= HandheldFriendlyMeta && type <= ViewportMeta; }
     bool isMetaViewportType() const { return type == ViewportMeta; }
     bool isSpecifiedByAuthor() const { return type != UserAgentStyleSheet; }
 
 private:
     enum Direction { Horizontal, Vertical };
     static float resolveViewportLength(const Length&, const FloatSize& initialViewportSize, Direction);
 };
 
 } // namespace WebCore
 
 #endif // ViewportDescription_h