Make sure tile textures are synchronized for D3D11. (bug 1119066, r=mattwoodrow)

--HG--
extra : rebase_source : 89d5654e43eb2a111a56c1432b90cd3a283f4a50

gfx/layers/client/TiledContentClient.cpp

@@ -1287,6 +1287,7 @@ ClientTiledLayerBuffer::ValidateTile(TileClient aTile,
 
   backBuffer->SetWaste(tileRegion.Area() * mResolution * mResolution);
   backBuffer->Unlock();
+  backBuffer->SyncWithObject(mCompositableClient->GetForwarder()->GetSyncObject());
 
   if (createdTextureClient) {
     if (!mCompositableClient->AddTextureClient(backBuffer)) {