Bug 722972 - Reduce about:memory perturbation (part 2 of 7). r=jlebar.

--HG--
extra : rebase_source : 3c8b59d8c2e55acd5eca32a984da344051869f43

toolkit/components/aboutmemory/content/aboutMemory.js

@@ -230,8 +230,8 @@ Reporter.prototype = {
   treeNameMatches: function(aTreeName) {
     // Nb: the '/' must be present, because we have a KIND_OTHER reporter
     // called "explicit" which is not part of the "explicit" tree.
-    aTreeName += "/";
-    return this._unsafePath.slice(0, aTreeName.length) === aTreeName;
+    return this._unsafePath.indexOf(aTreeName) === 0 &&
+           this._unsafePath.charAt(aTreeName.length) === '/';
   }
 };