Bug 1248496 - Show which DXVA API is being used in about:support. r=jya

dom/media/fmp4/MP4Decoder.cpp

@@ -270,10 +270,10 @@ MP4Decoder::IsVideoAccelerated(layers::LayersBackend aBackend, nsIGlobalObject*
                result.AssignLiteral("Yes");
              } else {
                result.AssignLiteral("No");
-               if (failureReason.Length()) {
-                 result.AppendLiteral("; ");
-                 AppendUTF8toUTF16(failureReason, result);
-               }
+             }
+             if (failureReason.Length()) {
+               result.AppendLiteral("; ");
+               AppendUTF8toUTF16(failureReason, result);
              }
              decoder->Shutdown();
              taskQueue->BeginShutdown();

dom/media/platforms/wmf/WMFVideoMFTManager.cpp

@@ -216,6 +216,14 @@ WMFVideoMFTManager::Init()
     mDXVAFailureReason.Append(d3d11Failure);
   }
 
+  if (success && mDXVA2Manager) {
+    if (mDXVA2Manager->IsD3D11()) {
+      mDXVAFailureReason.AssignLiteral("Using D3D11 API");
+    } else {
+      mDXVAFailureReason.AssignLiteral("Using D3D9 API");
+    }
+  }
+
   return success;
 }