Use a dirty bit in StyleSheetCollection::updateActiveStyleSheets.

sky/engine/core/dom/StyleSheetCollection.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, 2010, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
@@ skipping 21 matching lines @@
 #include "sky/engine/core/dom/Document.h"
 #include "sky/engine/core/dom/StyleEngine.h"
 #include "sky/engine/core/dom/shadow/ShadowRoot.h"
 #include "sky/engine/core/dom/TreeScope.h"
 #include "sky/engine/core/html/HTMLStyleElement.h"
 
 namespace blink {
 
 StyleSheetCollection::StyleSheetCollection(TreeScope& treeScope)
     : m_treeScope(treeScope)
+    , m_needsUpdate(true)
 {
 }
 
 StyleSheetCollection::~StyleSheetCollection()
 {
 }
 
 void StyleSheetCollection::addStyleSheetCandidateNode(HTMLStyleElement& element)
 {
     ASSERT(element.inActiveDocument());
     m_styleSheetCandidateNodes.add(&element);
+    m_needsUpdate = true;
 }
 
 void StyleSheetCollection::removeStyleSheetCandidateNode(HTMLStyleElement& element)
 {
     m_styleSheetCandidateNodes.remove(&element);
+    m_needsUpdate = true;
 }
 
 void StyleSheetCollection::collectStyleSheets(Vector<RefPtr<CSSStyleSheet>>& sheets)
 {
     for (Node* node : m_styleSheetCandidateNodes) {
         ASSERT(isHTMLStyleElement(*node));
         if (CSSStyleSheet* sheet = toHTMLStyleElement(node)->sheet())
             sheets.append(sheet);
     }
 }
 
 void StyleSheetCollection::updateActiveStyleSheets(StyleEngine* engine)
 {
+    // TODO(esprehn): We need to check if the resolver exists otherwise style
+    // doesn't get computed right. We should figure out why.
+    if (!m_needsUpdate && engine->resolver())
+        return;
+
     Vector<RefPtr<CSSStyleSheet>> candidateSheets;
     collectStyleSheets(candidateSheets);
 
     Node& root = m_treeScope.rootNode();
 
     // TODO(esprehn): Remove special casing for Document.
     if (root.isDocumentNode()) {
         engine->clearResolver();
         // FIMXE: The following depends on whether StyleRuleFontFace was modified or not.
         // No need to always-clear font cache.
         engine->clearFontCache();
     } else if (StyleResolver* styleResolver = engine->resolver()) {
         // We should not destroy StyleResolver when we find any stylesheet update in a shadow tree.
         // In this case, we will reset rulesets created from style elements in the shadow tree.
         m_treeScope.scopedStyleResolver().resetAuthorStyle();
         styleResolver->removePendingAuthorStyleSheets(m_activeAuthorStyleSheets);
         styleResolver->lazyAppendAuthorStyleSheets(0, candidateSheets);
     }
 
     // TODO(esprehn): We should avoid subtree recalcs in sky when rules change
     // and only recalc specific tree scopes.
     root.setNeedsStyleRecalc(SubtreeStyleChange);
 
     // TODO(esprehn): We should use LocalStyleChange, :host rule changes
     // can only impact the host directly as Sky has no descendant selectors.
     if (root.isShadowRoot())
         toShadowRoot(root).host()->setNeedsStyleRecalc(SubtreeStyleChange);
 
     m_activeAuthorStyleSheets.swap(candidateSheets);
+    m_needsUpdate = false;
 }
 
 }