Bug 586562: Always use A8R8G8B8 for our swap chains. Fixes black chrome for NVidia. r=vlad a=mossop

gfx/layers/d3d9/DeviceManagerD3D9.cpp

@@ -85,7 +85,7 @@ SwapChainD3D9::Init(HWND hWnd)
   D3DPRESENT_PARAMETERS pp;
   memset(&pp, 0, sizeof(D3DPRESENT_PARAMETERS));
 
-  pp.BackBufferFormat = D3DFMT_UNKNOWN;
+  pp.BackBufferFormat = D3DFMT_A8R8G8B8;
   pp.SwapEffect = D3DSWAPEFFECT_COPY;
   pp.Windowed = TRUE;
   pp.PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;