[WIP] Find out if ElementResolveContext(Document&) is reachable.

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 521 matching lines @@
 // Start loading resources referenced by this style.
 void StyleResolver::loadPendingResources(StyleResolverState& state)
 {
     m_styleResourceLoader.loadPendingResources(state.style(), state.elementStyleResources());
     document().styleEngine()->fontSelector()->fontLoader()->loadPendingFonts();
 }
 
 PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderStyle* defaultParent, StyleSharingBehavior sharingBehavior,
     RuleMatchingBehavior matchingBehavior)
 {
+    ASSERT(element);
     ASSERT(document().frame());
     ASSERT(document().settings());
     ASSERT(!hasPendingAuthorStyleSheets());
     ASSERT(!m_needCollectFeatures);
 
     // Once an element has a renderer, we don't try to destroy it, since otherwise the renderer
     // will vanish if a style recalc happens during loading.
     if (sharingBehavior == AllowStyleSharing && !document().isRenderingReady() && !element->renderer()) {
         if (!s_styleNotYetAvailable) {
             s_styleNotYetAvailable = RenderStyle::create().leakRef();
@@ skipping 302 matching lines @@
     if (PseudoElement* pseudoElement = element->pseudoElement(pseudoStyleRequest.pseudoId))
         setAnimationUpdateIfNeeded(state, *pseudoElement);
 
     // Now return the style.
     return state.takeStyle();
 }
 
 PassRefPtr<RenderStyle> StyleResolver::styleForPage(int pageIndex)
 {
     ASSERT(!hasPendingAuthorStyleSheets());
+    ASSERT(document().documentElement());
     StyleResolverState state(document(), document().documentElement()); // m_rootElementStyle will be set to the document style.
 
     RefPtr<RenderStyle> style = RenderStyle::create();
     const RenderStyle* rootElementStyle = state.rootElementStyle() ? state.rootElementStyle() : document().renderStyle();
     ASSERT(rootElementStyle);
     style->inheritFrom(rootElementStyle);
     state.setStyle(style.release());
 
     PageRuleCollector collector(rootElementStyle, pageIndex);
 
@@ skipping 675 matching lines @@
     if (!m_styleResolverStats)
         return;
     fprintf(stderr, "=== Style Resolver Stats (resolve #%u) (%s) ===\n", ++m_styleResolverStatsSequence, document().url().string().utf8().data());
     fprintf(stderr, "%s\n", m_styleResolverStats->report().utf8().data());
     fprintf(stderr, "== Totals ==\n");
     fprintf(stderr, "%s\n", m_styleResolverStatsTotals->report().utf8().data());
 }
 
 void StyleResolver::applyPropertiesToStyle(const CSSPropertyValue* properties, size_t count, RenderStyle* style)
 {
+    ASSERT(document().documentElement());
     StyleResolverState state(document(), document().documentElement(), style);
     state.setStyle(style);
 
     for (size_t i = 0; i < count; ++i) {
         if (properties[i].value) {
             // As described in BUG66291, setting font-size and line-height on a font may entail a CSSPrimitiveValue::computeLengthDouble call,
             // which assumes the fontMetrics are available for the affected font, otherwise a crash occurs (see http://trac.webkit.org/changeset/96122).
             // The updateFont() call below updates the fontMetrics and ensure the proper setting of font-size and line-height.
             switch (properties[i].property) {
             case CSSPropertyFontSize:
@@ skipping 35 matching lines @@
     visitor->trace(m_uncommonAttributeRuleSet);
     visitor->trace(m_watchedSelectorsRules);
     visitor->trace(m_treeBoundaryCrossingRules);
     visitor->trace(m_styleSharingLists);
     visitor->trace(m_pendingStyleSheets);
     visitor->trace(m_document);
 #endif
 }
 
 } // namespace blink