Bug 1062492. Only use DIBTextureClient with cairo drawing. r=bas

We don't want DIBTextureClient unless we're going to be using cairo for
drawing.

gfx/layers/client/TextureClient.cpp

@@ -291,7 +291,8 @@ TextureClient::CreateForDrawing(ISurfaceAllocator* aAllocator,
   }
 
   if (!texture && aFormat == SurfaceFormat::B8G8R8X8 &&
-      aAllocator->IsSameProcess()) {
+      aAllocator->IsSameProcess() &&
+      aMoz2DBackend == gfx::BackendType::CAIRO) {
     texture = new DIBTextureClient(aFormat, aTextureFlags);
   }