Bug 1307223 - Don't warning multiple times about WMF dlls failing to load. r=cpearce

We already report failure in |LoadDlls| on the initial failure to load, there's
no need to warn more than once per session.

MozReview-Commit-ID: FhsR2ZaMSLT

--HG--
extra : rebase_source : ae7d94af5c9d9253b82b2d45dc6967b5b21c6492

dom/media/platforms/wmf/WMFUtils.cpp

@@ -203,7 +203,9 @@ HRESULT
 MFStartup()
 {
   HRESULT hr = LoadDLLs();
-  NS_ENSURE_TRUE(SUCCEEDED(hr), hr);
+  if (FAILED(hr)) {
+    return hr;
+  }
 
   const int MF_VISTA_VERSION = (0x0001 << 16 | MF_API_VERSION);
   const int MF_WIN7_VERSION = (0x0002 << 16 | MF_API_VERSION);