Check for styleResolver() in preparation for async style update.

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

Index: third_party/WebKit/Source/core/css/resolver/ScopedStyleResolver.cpp
diff --git a/third_party/WebKit/Source/core/css/resolver/ScopedStyleResolver.cpp b/third_party/WebKit/Source/core/css/resolver/ScopedStyleResolver.cpp
index 28002081509a319e7f99781742b4be18c31b3f2e..461a30f564862cd27472d2b7cb7105bb9acaebe0 100644
--- a/third_party/WebKit/Source/core/css/resolver/ScopedStyleResolver.cpp
+++ b/third_party/WebKit/Source/core/css/resolver/ScopedStyleResolver.cpp
@@ -79,7 +79,7 @@ void ScopedStyleResolver::addFontFaceRules(const RuleSet& ruleSet) {
       cssFontSelector->fontFaceCache()->add(cssFontSelector, fontFaceRule,
                                             fontFace);
   }
-  if (fontFaceRules.size())
+  if (fontFaceRules.size() && document.styleResolver())
     document.styleResolver()->invalidateMatchedPropertiesCache();
 }