Bug 1172010 - Fix promise loader path. r=jwalker

toolkit/devtools/Loader.jsm

@@ -152,7 +152,7 @@ SrcdirProvider.prototype = {
     let contentObserverURI = this.fileURI(OS.Path.join(toolkitDir), "content-observer.js");
     let gcliURI = this.fileURI(OS.Path.join(toolkitDir, "gcli", "source", "lib", "gcli"));
     let projecteditorURI = this.fileURI(OS.Path.join(devtoolsDir, "projecteditor"));
-    let promiseURI = this.fileURI(OS.Path.join(modulesDir, "promise-backend.js"));
+    let promiseURI = this.fileURI(OS.Path.join(modulesDir, "Promise-backend.js"));
     let acornURI = this.fileURI(OS.Path.join(toolkitDir, "acorn"));
     let acornWalkURI = OS.Path.join(acornURI, "walk.js");
     let ternURI = OS.Path.join(toolkitDir, "tern");