Fix assert when resolving font on canvas with dirty shadow distribution

third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 2004-2005 Allan Sandfeld Jensen (kde@carewolf.com)
  * Copyright (C) 2006, 2007 Nicholas Shanks (webkit@nickshanks.com)
  * Copyright (C) 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012, 2013 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  * Copyright (C) 2007, 2008 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (c) 2011, Code Aurora Forum. All rights reserved.
  * Copyright (C) Research In Motion Limited 2011. All rights reserved.
@@ skipping 1430 matching lines @@
     CSSPropertyID properties[] = {
         CSSPropertyFontSize,
         CSSPropertyFontFamily,
         CSSPropertyFontStretch,
         CSSPropertyFontStyle,
         CSSPropertyFontVariant,
         CSSPropertyFontWeight,
         CSSPropertyLineHeight,
     };
 
     // TODO(timloh): This is weird, the style is being used as its own parent

[rune, 2015/09/23 22:55:42]

This seems to be because style object already has the default size of 10px and
relative units are supposed to be resolved against that default size when the
canvas is not in the tree (according to
http://www.w3.org/TR/2dcontext/#text-styles).

That's not correct for canvases in the document tree if I read the spec
correctly, but that would be another CL.

-    StyleResolverState state(document(), document().documentElement(), style);
+    StyleResolverState state(document(), nullptr, style);
     state.setStyle(style);
 
     for (CSSPropertyID property : properties) {
         if (property == CSSPropertyLineHeight)
             updateFont(state);
         StyleBuilder::applyProperty(property, state, propertySet.getPropertyCSSValue(property).get());
     }
 }
 
 void StyleResolver::addMediaQueryResults(const MediaQueryResultList& list)
@@ skipping 24 matching lines @@
     visitor->trace(m_watchedSelectorsRules);
     visitor->trace(m_treeBoundaryCrossingRules);
     visitor->trace(m_styleResourceLoader);
     visitor->trace(m_styleSharingLists);
     visitor->trace(m_pendingStyleSheets);
     visitor->trace(m_document);
 #endif
 }
 
 } // namespace blink