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

Source/core/css/resolver/StyleResolver.cpp

Index: Source/core/css/resolver/StyleResolver.cpp
diff --git a/Source/core/css/resolver/StyleResolver.cpp b/Source/core/css/resolver/StyleResolver.cpp
index e1db3dd6d754f30ebefbfdfc04b2668486223516..c0aa3eb11c2607cb41bc8fc677f7934f97f4f48a 100644
--- a/Source/core/css/resolver/StyleResolver.cpp
+++ b/Source/core/css/resolver/StyleResolver.cpp
@@ -539,6 +539,7 @@ void StyleResolver::loadPendingResources(StyleResolverState& state)
 PassRefPtr<RenderStyle> StyleResolver::styleForElement(Element* element, RenderStyle* defaultParent, StyleSharingBehavior sharingBehavior,
     RuleMatchingBehavior matchingBehavior)
 {
+    ASSERT(element);
     ASSERT(document().frame());
     ASSERT(document().settings());
     ASSERT(!hasPendingAuthorStyleSheets());
@@ -861,6 +862,7 @@ PassRefPtr<RenderStyle> StyleResolver::pseudoStyleForElement(Element* element, c
 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();
@@ -1556,6 +1558,7 @@ void StyleResolver::printStats()
 
 void StyleResolver::applyPropertiesToStyle(const CSSPropertyValue* properties, size_t count, RenderStyle* style)
 {
+    ASSERT(document().documentElement());
     StyleResolverState state(document(), document().documentElement(), style);
     state.setStyle(style);