bug 1242268 use pointers instead of copies of string literals in AudioNode memory reporting r=padenot

MozReview-Commit-ID: E85FGrmfOWI

--HG--
extra : rebase_source : 0895e91ca000164f70251ae0fbb61fcca39cbe56

dom/media/MediaStreamGraph.cpp

@@ -3548,8 +3548,8 @@ MediaStreamGraphImpl::CollectReports(nsIHandleReportCallback* aHandleReport,
 
   for (size_t i = 0; i < mAudioStreamSizes.Length(); i++) {
     const AudioNodeSizes& usage = mAudioStreamSizes[i];
-    const char* const nodeType =  usage.mNodeType.IsEmpty() ?
-                                  "<unknown>" : usage.mNodeType.get();
+    const char* const nodeType =
+      usage.mNodeType ? usage.mNodeType : "<unknown>";
 
     nsPrintfCString domNodePath("explicit/webaudio/audio-node/%s/dom-nodes",
                                 nodeType);

dom/media/MediaStreamGraph.h

@@ -153,7 +153,7 @@ struct AudioNodeSizes
   size_t mDomNode;
   size_t mStream;
   size_t mEngine;
-  nsCString mNodeType;
+  const char* mNodeType;
 };
 
 class AudioNodeEngine;

dom/media/webaudio/AudioNode.h

@@ -217,6 +217,8 @@ public:
   virtual size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const;
   virtual size_t SizeOfIncludingThis(MallocSizeOf aMallocSizeOf) const;
 
+  // Returns a string from constant static storage identifying the dom node
+  // type.
   virtual const char* NodeType() const = 0;
 
 private: