[cc] Remove BeginFrameAck from BFS::DidFinishFrame and update tests.

components/exo/surface_unittest.cc

Index: components/exo/surface_unittest.cc
diff --git a/components/exo/surface_unittest.cc b/components/exo/surface_unittest.cc
index 1eb280384a911471422f8c4c89eb083b1161bbbb..7e9ad528b3ccd42e1fda774060f0c05ec014b1c1 100644
--- a/components/exo/surface_unittest.cc
+++ b/components/exo/surface_unittest.cc
@@ -339,15 +339,15 @@ TEST_F(SurfaceTest, SendsBeginFrameAcks) {
   source.TestOnBeginFrame(args);  // Runs the frame callback.
   EXPECT_EQ(args.frame_time, frame_time);
 
-  surface->Commit();  // Acknowledges the BeginFrame.
+  surface->Commit();  // Acknowledges the BeginFrame via CompositorFrame.
   RunAllPendingInMessageLoop();
 
+  const cc::CompositorFrame& frame = GetFrameFromSurface(surface.get());
   cc::BeginFrameAck expected_ack(args.source_id, args.sequence_number,
                                  args.sequence_number, true);
-  EXPECT_EQ(expected_ack, source.LastAckForObserver(surface.get()));
-
-  const cc::CompositorFrame& frame = GetFrameFromSurface(surface.get());
   EXPECT_EQ(expected_ack, frame.metadata.begin_frame_ack);
+
+  // TODO(eseckler): Add test for DidNotProduceFrame plumbing.
 }
 
 }  // namespace