Initialize member array field.

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

Index: third_party/WebKit/Source/core/css/RuleSet.cpp
diff --git a/third_party/WebKit/Source/core/css/RuleSet.cpp b/third_party/WebKit/Source/core/css/RuleSet.cpp
index bf5ffe0d80110b34e23a9a8cee280fa1eeada4dd..5ad310f6ac30424484b17c5e82a41a9adffcb1d6 100644
--- a/third_party/WebKit/Source/core/css/RuleSet.cpp
+++ b/third_party/WebKit/Source/core/css/RuleSet.cpp
@@ -129,7 +129,8 @@ RuleData::RuleData(StyleRule* rule,
       m_linkMatchType(selector().computeLinkMatchType()),
       m_hasDocumentSecurityOrigin(addRuleFlags & RuleHasDocumentSecurityOrigin),
       m_propertyWhitelist(
-          determinePropertyWhitelistType(addRuleFlags, selector())) {
+          determinePropertyWhitelistType(addRuleFlags, selector())),
+      m_descendantSelectorIdentifierHashes() {
   SelectorFilter::collectIdentifierHashes(
       selector(), m_descendantSelectorIdentifierHashes, maximumIdentifierCount);
 }