Avoid nuking everything when injecting stylesheet.

third_party/WebKit/Source/core/dom/StyleEngine.cpp

 /*
  * 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, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 139 matching lines @@
     m_usesSiblingRules = features.usesSiblingRules();
     m_usesFirstLineRules = features.usesFirstLineRules();
     m_usesWindowInactiveSelector = features.usesWindowInactiveSelector();
     m_maxDirectAdjacentSelectors = features.maxDirectAdjacentSelectors();
 }
 
 void StyleEngine::injectAuthorSheet(PassRefPtrWillBeRawPtr<StyleSheetContents> authorSheet)
 {
     m_injectedAuthorStyleSheets.append(CSSStyleSheet::create(authorSheet, m_document));
     markDocumentDirty();
-    resolverChanged(FullStyleUpdate);
+    resolverChanged(AnalyzedStyleUpdate);
 }
 
 void StyleEngine::addPendingSheet()
 {
     m_pendingStylesheets++;
 }
 
 // This method is called whenever a top-level stylesheet has finished loading.
 void StyleEngine::removePendingSheet(Node* styleSheetCandidateNode)
 {
@@ skipping 564 matching lines @@
     visitor->trace(m_dirtyTreeScopes);
     visitor->trace(m_activeTreeScopes);
     visitor->trace(m_fontSelector);
     visitor->trace(m_textToSheetCache);
     visitor->trace(m_sheetToTextCache);
 #endif
     CSSFontSelectorClient::trace(visitor);
 }
 
 } // namespace blink