Fix assert when resolving font on canvas with dirty shadow distribution

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

Index: third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
index a458301f00cc6e5abc97587a93b11bd14aa07d44..71bf96ea8ac9e1b5c93c32921f727cd7f4d19600 100644
--- a/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/StyleResolver.cpp
@@ -1449,7 +1449,7 @@ void StyleResolver::computeFont(ComputedStyle* style, const StylePropertySet& pr
     };
 
     // 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) {