Don't use gfxPlatform for creating temporary surfaces in the BasicCompositor. (bug 1311770, r=mattwoodrow)

gfx/layers/basic/BasicCompositor.cpp

@@ -571,7 +571,7 @@ BasicCompositor::DrawQuad(const gfx::Rect& aRect,
     newTransform = aTransform.As2D();
   } else {
     // Create a temporary surface for the transform.
-    dest = gfxPlatform::GetPlatform()->CreateOffscreenContentDrawTarget(RoundedOut(aRect).Size(), SurfaceFormat::B8G8R8A8);
+    dest = Factory::CreateDrawTarget(gfxVars::ContentBackend(), RoundedOut(aRect).Size(), SurfaceFormat::B8G8R8A8);
     if (!dest) {
       return;
     }