Revert of document.querySelector[All]() should check selector context...

Revert of document.querySelector[All]() should check selector context (patchset #6 id:100001 of https://codereview.chromium.org/1245933002/ )

Reason for revert:
This seems to have caused a significant perf
regression.  Reverting.

BUG=526742

Original issue's description:
> document.querySelector[All]() should check selector context
> 
> Blink failed to check whether the left-most matched selector ends up
> in Document TreeScope.
> The check was only enabled for querySelector*() is called on
> a regular element, not on document.
> 
> This issue can be exposed by passing "::shadow" or "/deep/"
> which pierces shadow boundary and the selector can
> incorrectly match inside shadow.
> 
> BUG=511486
> TEST=fast/dom/shadow/querySelector-with-shadow-all-and-shadow-deep.html
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201461

TBR=esprehn@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=511486

Review URL: https://codereview.chromium.org/1329523002

git-svn-id: svn://svn.chromium.org/blink/trunk@201514 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/LayoutTests/fast/dom/shadow/querySelector-with-shadow-all-and-shadow-deep-expected.txt

@@ -50,10 +50,6 @@ PASS fooHost.querySelectorAll("::shadow span").length is 3
 PASS fooHost.querySelectorAll("::shadow span")[0].id is "not-top"
 PASS fooHost.querySelectorAll("::shadow span")[1].id is "top"
 PASS fooHost.querySelectorAll("::shadow span")[2].id is "inner-host"
-PASS document.querySelectorAll("::shadow span").length is 3
-PASS document.querySelectorAll("::shadow span")[0].id is "not-top"
-PASS document.querySelectorAll("::shadow span")[1].id is "top"
-PASS document.querySelectorAll("::shadow span")[2].id is "inner-host"
 PASS successfullyParsed is true
 
 TEST COMPLETE

third_party/WebKit/LayoutTests/fast/dom/shadow/querySelector-with-shadow-all-and-shadow-deep.html

@@ -82,10 +82,4 @@ shouldBe('fooHost.querySelectorAll("::shadow span").length', '3');
 shouldBe('fooHost.querySelectorAll("::shadow span")[0].id', '"not-top"');
 shouldBe('fooHost.querySelectorAll("::shadow span")[1].id', '"top"');
 shouldBe('fooHost.querySelectorAll("::shadow span")[2].id', '"inner-host"');
-
-// crbug.com/511486
-shouldBe('document.querySelectorAll("::shadow span").length', '3');
-shouldBe('document.querySelectorAll("::shadow span")[0].id', '"not-top"');
-shouldBe('document.querySelectorAll("::shadow span")[1].id', '"top"');
-shouldBe('document.querySelectorAll("::shadow span")[2].id', '"inner-host"');
 </script>

third_party/WebKit/Source/core/css/SelectorChecker.cpp

@@ -960,9 +960,9 @@ bool SelectorChecker::checkPseudoClass(const SelectorCheckingContext& context, M
     case CSSSelector::PseudoScope:
         if (m_mode == SharingRules)
             return true;
-        if (context.scope == element.document())
-            return element == element.document().documentElement();
-        return context.scope == element;
+        if (context.scope)
+            return context.scope == element;
+        return element == element.document().documentElement();
     case CSSSelector::PseudoUnresolved:
         return element.isUnresolvedCustomElement();
     case CSSSelector::PseudoHost:
@@ -1050,6 +1050,8 @@ bool SelectorChecker::checkPseudoHost(const SelectorCheckingContext& context, Ma
     if (m_mode == SharingRules)
         return true;
     // :host only matches a shadow host when :host is in a shadow tree of the shadow host.
+    if (!context.scope)
+        return false;
     const ContainerNode* shadowHost = context.scope->shadowHost();
     if (!shadowHost || shadowHost != element)
         return false;

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

@@ -122,8 +122,9 @@ inline bool SelectorDataList::selectorMatches(const CSSSelector& selector, Eleme
     SelectorChecker selectorChecker(SelectorChecker::QueryingRules);
     SelectorChecker::SelectorCheckingContext selectorCheckingContext(&element, SelectorChecker::VisitedMatchDisabled);
     selectorCheckingContext.selector = &selector;
-    selectorCheckingContext.scope = &rootNode;
-    selectorCheckingContext.scopeContainsLastMatchedElement = true;
+    selectorCheckingContext.scope = !rootNode.isDocumentNode() ? &rootNode : nullptr;
+    if (selectorCheckingContext.scope)
+        selectorCheckingContext.scopeContainsLastMatchedElement = true;
     return selectorChecker.match(selectorCheckingContext);
 }