Check for null selectors when looping in findBestRuleSetAndAdd

Source/core/css/RuleSet.cpp

Index: Source/core/css/RuleSet.cpp
diff --git a/Source/core/css/RuleSet.cpp b/Source/core/css/RuleSet.cpp
index fefc1e4310b1aa9006b8ffcfa65737dd361a0a0b..0f452c9b46e783ea771523386f78a0e847cf8bb1 100644
--- a/Source/core/css/RuleSet.cpp
+++ b/Source/core/css/RuleSet.cpp
@@ -177,10 +177,11 @@ bool RuleSet::findBestRuleSetAndAdd(const CSSSelector& component, RuleData& rule
 #endif
 
     const CSSSelector* it = &component;
-    for (; it->relation() == CSSSelector::SubSelector; it = it->tagHistory()) {
+    for (; it && it->relation() == CSSSelector::SubSelector; it = it->tagHistory()) {
         extractValuesforSelector(it, id, className, customPseudoElementName, tagName);
     }
-    extractValuesforSelector(it, id, className, customPseudoElementName, tagName);
+    if (it)

[ojan, 2014/04/01 21:20:50]

This makes me sad. I'm OK with the patch to fix the P1 bug, but can we add a
FIXME to make inputtext not do crazy so that we can keep the system simpler and
not need these null-checks.

[chrishtr, 2014/04/01 21:27:58]

Done.

+        extractValuesforSelector(it, id, className, customPseudoElementName, tagName);
 
     // Prefer rule sets in order of most likely to apply infrequently.
     if (!id.isEmpty()) {