Handle ::content and :host-context correctly in SelectorQuery.

Source/core/dom/SelectorQuery.cpp

Index: Source/core/dom/SelectorQuery.cpp
diff --git a/Source/core/dom/SelectorQuery.cpp b/Source/core/dom/SelectorQuery.cpp
index 15dcc963ccc0c6048fa55f6d27e44c0df6039a0e..4b0b089811d028f870fa4a5d25fad07d12bf4a44 100644
--- a/Source/core/dom/SelectorQuery.cpp
+++ b/Source/core/dom/SelectorQuery.cpp
@@ -107,11 +107,13 @@ void SelectorDataList::initialize(const CSSSelectorList& selectorList)
         selectorCount++;
 
     m_crossesTreeBoundary = false;
+    m_needsUpdatedDistribution = false;
     m_selectors.reserveInitialCapacity(selectorCount);
     unsigned index = 0;
     for (const CSSSelector* selector = selectorList.first(); selector; selector = CSSSelectorList::next(*selector), ++index) {
         m_selectors.uncheckedAppend(selector);
         m_crossesTreeBoundary |= selectorList.selectorCrossesTreeScopes(index);
+        m_needsUpdatedDistribution |= selectorList.selectorNeedsUpdatedDistribution(index);
     }
 }
 
@@ -128,6 +130,9 @@ inline bool SelectorDataList::selectorMatches(const CSSSelector& selector, Eleme
 
 bool SelectorDataList::matches(Element& targetElement) const
 {
+    if (m_needsUpdatedDistribution)
+        targetElement.updateDistribution();

[kochi, 2015/05/25 11:07:04]

At first I wondered why after updateDistribution() m_needsUpdatedDistribution
isn't
cleared, but now I suppose all the members in SelectorDataList are immutable
after
initialize() is done.

Then I have a question that if this data is cached in SelectorQueryCache, the
m_needsUpdatedDistribution is also cached, right?
Does it have any issue, once it is cached with m_needsUpdatedDistribution =
false,
then some shadow tree state is changed and the same query is given?

SelectorQueryCache::invalidate() looks called only from Document.cpp,
setCompatibilityMode() and updateBaseURL().

[esprehn, 2015/05/25 20:52:26]

SelectorQuery is just a "query plan", it's how the query should be executed, not
something dynamic that should reset it's bits. The only time these plans need to
be updated is when the way the selector was parsed could have changed, which is
when the document mode or uri could have changed that's why those are the places
we call invalidate().

[kochi, 2015/05/26 00:59:05]

Thanks, I understand.

+
     unsigned selectorCount = m_selectors.size();
     for (unsigned i = 0; i < selectorCount; ++i) {
         if (selectorMatches(*m_selectors[i], targetElement, targetElement))
@@ -139,6 +144,9 @@ bool SelectorDataList::matches(Element& targetElement) const
 
 Element* SelectorDataList::closest(Element& targetElement) const
 {
+    if (m_needsUpdatedDistribution)
+        targetElement.updateDistribution();
+
     unsigned selectorCount = m_selectors.size();
     for (Element* currentElement = &targetElement; currentElement; currentElement = currentElement->parentElement()) {
         for (unsigned i = 0; i < selectorCount; ++i) {
@@ -207,7 +215,15 @@ void SelectorDataList::collectElementsByTagName(ContainerNode& rootNode, const Q
 
 inline bool SelectorDataList::canUseFastQuery(const ContainerNode& rootNode) const
 {
-    return m_selectors.size() == 1 && !m_crossesTreeBoundary && rootNode.inDocument() && !rootNode.document().inQuirksMode();
+    if (m_crossesTreeBoundary)
+        return false;
+    if (m_needsUpdatedDistribution)
+        return false;
+    if (rootNode.document().inQuirksMode())
+        return false;
+    if (!rootNode.inDocument())
+        return false;
+    return m_selectors.size() == 1;
 }
 
 inline bool ancestorHasClassName(ContainerNode& rootNode, const AtomicString& className)
@@ -439,8 +455,9 @@ template <typename SelectorQueryTrait>
 void SelectorDataList::execute(ContainerNode& rootNode, typename SelectorQueryTrait::OutputType& output) const
 {
     if (!canUseFastQuery(rootNode)) {
-        if (m_crossesTreeBoundary) {
+        if (m_needsUpdatedDistribution)
             rootNode.updateDistribution();
+        if (m_crossesTreeBoundary) {
             executeSlowTraversingShadowTree<SelectorQueryTrait>(rootNode, output);
         } else {
             executeSlow<SelectorQueryTrait>(rootNode, output);