Bug 1383756 - Avoid excessive AddRef()ing of atoms in nsNodeInfoManager::GetNodeInfo(); r=baku

We make the NodeInfoInner members raw pointers, and AddRef/Release
them manally in the constructor/destructor of NodeInfo, and in the
cases where NodeInfoInner objects are created for hashtable lookups,
no further refcounting is performed.

dom/base/NodeInfo.cpp

@@ -36,6 +36,13 @@ using mozilla::dom::NodeInfo;
 NodeInfo::~NodeInfo()
 {
   mOwnerManager->RemoveNodeInfo(this);
+
+  // We can't use NS_IF_RELEASE because mName is const.
+  if (mInner.mName) {
+    mInner.mName->Release();
+  }
+  NS_IF_RELEASE(mInner.mPrefix);
+  NS_IF_RELEASE(mInner.mExtraName);
 }
 
 NodeInfo::NodeInfo(nsIAtom *aName, nsIAtom *aPrefix, int32_t aNamespaceID,
@@ -47,6 +54,10 @@ NodeInfo::NodeInfo(nsIAtom *aName, nsIAtom *aPrefix, int32_t aNamespaceID,
 {
   CheckValidNodeInfo(aNodeType, aName, aNamespaceID, aExtraName);
 
+  NS_IF_ADDREF(mInner.mName);
+  NS_IF_ADDREF(mInner.mPrefix);
+  NS_IF_ADDREF(mInner.mExtraName);
+
   // Now compute our cached members.
 
   // Qualified name.  If we have no prefix, use ToString on

dom/base/NodeInfo.h

@@ -265,12 +265,12 @@ protected:
     {
     }
 
-    const nsCOMPtr<nsIAtom> mName;
+    nsIAtom* const MOZ_OWNING_REF mName;
-    nsCOMPtr<nsIAtom> mPrefix;
+    nsIAtom* MOZ_OWNING_REF mPrefix;
     int32_t             mNamespaceID;
     uint16_t            mNodeType; // As defined by nsIDOMNode.nodeType
     const nsAString* const mNameString;
-    nsCOMPtr<nsIAtom> mExtraName; // Only used by PIs and DocTypes
+    nsIAtom* MOZ_OWNING_REF mExtraName; // Only used by PIs and DocTypes
     PLHashNumber      mHash;
     bool              mHashInitialized;
   };