Bug 952721 - Don't crash if our surface allocation fails in TiledContentClient. r=Bas

gfx/layers/client/TiledContentClient.cpp

@@ -665,6 +665,10 @@ ClientTiledLayerBuffer::PaintThebes(const nsIntRegion& aNewValidRegion,
                        ceilf(bounds.height * mResolution)),
           gfx::ImageFormatToSurfaceFormat(format));
 
+      if (!mSinglePaintDrawTarget) {
+        return;
+      }
+
       ctxt = new gfxContext(mSinglePaintDrawTarget);
 
       mSinglePaintBufferOffset = nsIntPoint(bounds.x, bounds.y);