Read the default min-width value from the UA style sheets

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 2815 matching lines @@
     // isn't set at the end of a layout.
     if (view->needsLayout())
         view->layout();
 }
 
 void WebViewImpl::updatePageDefinedViewportConstraints(const ViewportDescription& description)
 {
     if (!settings()->viewportEnabled() || !page() || (!m_size.width && !m_size.height))
         return;
 
+    Document* document = page()->mainFrame()->document();
+
+    Length defaultMinWidth = document->viewportDefaultMinWidth();
+    if (defaultMinWidth.isAuto())
+        defaultMinWidth = Length(ExtendToZoom);
+
     ViewportDescription adjustedDescription = description;
     if (settingsImpl()->viewportMetaLayoutSizeQuirk() && adjustedDescription.type == ViewportDescription::ViewportMeta) {
-        if (adjustedDescription.maxWidth.type() == ExtendToZoom)
-            adjustedDescription.maxWidth = Length(); // auto
         const int legacyWidthSnappingMagicNumber = 320;
         if (adjustedDescription.maxWidth.isFixed() && adjustedDescription.maxWidth.value() <= legacyWidthSnappingMagicNumber)
             adjustedDescription.maxWidth = Length(DeviceWidth);
         if (adjustedDescription.maxHeight.isFixed() && adjustedDescription.maxHeight.value() <= m_size.height)
             adjustedDescription.maxHeight = Length(DeviceHeight);
         adjustedDescription.minWidth = adjustedDescription.maxWidth;
         adjustedDescription.minHeight = adjustedDescription.maxHeight;
     }
+
     float oldInitialScale = m_pageScaleConstraintsSet.pageDefinedConstraints().initialScale;
-    m_pageScaleConstraintsSet.updatePageDefinedConstraints(adjustedDescription, m_size);
+    m_pageScaleConstraintsSet.updatePageDefinedConstraints(adjustedDescription, m_size, defaultMinWidth);
 
     if (settingsImpl()->clobberUserAgentInitialScaleQuirk()
         && m_pageScaleConstraintsSet.userAgentConstraints().initialScale != -1
         && m_pageScaleConstraintsSet.userAgentConstraints().initialScale * deviceScaleFactor() <= 1) {
         if (description.maxWidth == Length(DeviceWidth)
-            || (description.maxWidth.type() == ExtendToZoom && m_pageScaleConstraintsSet.pageDefinedConstraints().initialScale == 1.0f))
+            || (description.maxWidth.type() == Auto && m_pageScaleConstraintsSet.pageDefinedConstraints().initialScale == 1.0f))
             setInitialPageScaleOverride(-1);
     }
-    m_pageScaleConstraintsSet.adjustForAndroidWebViewQuirks(adjustedDescription, m_size, page()->settings().layoutFallbackWidth(), deviceScaleFactor(), settingsImpl()->supportDeprecatedTargetDensityDPI(), page()->settings().wideViewportQuirkEnabled(), page()->settings().useWideViewport(), page()->settings().loadWithOverviewMode(), settingsImpl()->viewportMetaNonUserScalableQuirk());
+
+    m_pageScaleConstraintsSet.adjustForAndroidWebViewQuirks(adjustedDescription, m_size, defaultMinWidth.intValue(), deviceScaleFactor(), settingsImpl()->supportDeprecatedTargetDensityDPI(), page()->settings().wideViewportQuirkEnabled(), page()->settings().useWideViewport(), page()->settings().loadWithOverviewMode(), settingsImpl()->viewportMetaNonUserScalableQuirk());
     float newInitialScale = m_pageScaleConstraintsSet.pageDefinedConstraints().initialScale;
     if (oldInitialScale != newInitialScale && newInitialScale != -1) {
         m_pageScaleConstraintsSet.setNeedsReset(true);
         if (mainFrameImpl() && mainFrameImpl()->frameView())
             mainFrameImpl()->frameView()->setNeedsLayout();
     }
 
     updateMainFrameLayoutSize();
 }
 
@@ skipping 1134 matching lines @@
     const PageScaleConstraints& constraints = m_pageScaleConstraintsSet.pageDefinedConstraints();
 
     if (!mainFrameImpl() || !mainFrameImpl()->frameView())
         return false;
 
     return mainFrameImpl()->frameView()->layoutSize().width() == m_size.width
         || (constraints.minimumScale == constraints.maximumScale && constraints.minimumScale != -1);
 }
 
 } // namespace blink