Add case to verify the coexistence of primary Surface and fallback Surface

This test verifies that in the presence of both primary Surface and fallback
Surface, the fallback will not be used.

BUG=None
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2741613002
Cr-Commit-Position: refs/heads/master@{#455679}

cc/surfaces/surface_aggregator_unittest.cc

@@ -423,6 +423,67 @@ TEST_F(SurfaceAggregatorValidSurfaceTest, FallbackSurfaceReference) {
   fallback_child_factory.EvictSurface();
 }
 
+// This test verifies that in the presence of both primary Surface and fallback
+// Surface, the fallback will not be used.
+TEST_F(SurfaceAggregatorValidSurfaceTest, FallbackSurfaceReferenceWithPrimary) {
+  SurfaceFactory primary_child_factory(kArbitraryChildFrameSinkId1, &manager_,
+                                       &empty_client_);
+  LocalSurfaceId primary_child_local_surface_id = allocator_.GenerateId();
+  SurfaceId primary_child_surface_id(primary_child_factory.frame_sink_id(),
+                                     primary_child_local_surface_id);
+  test::Quad primary_child_quads[] = {
+      test::Quad::SolidColorQuad(SK_ColorGREEN)};
+  test::Pass primary_child_passes[] = {
+      test::Pass(primary_child_quads, arraysize(primary_child_quads))};
+
+  // Submit a CompositorFrame to the primary Surface containing a green
+  // SolidColorDrawQuad.
+  SubmitCompositorFrame(&primary_child_factory, primary_child_passes,
+                        arraysize(primary_child_passes),
+                        primary_child_local_surface_id);
+
+  SurfaceFactory fallback_child_factory(kArbitraryChildFrameSinkId2, &manager_,
+                                        &empty_client_);
+  LocalSurfaceId fallback_child_local_surface_id = allocator_.GenerateId();
+  SurfaceId fallback_child_surface_id(fallback_child_factory.frame_sink_id(),
+                                      fallback_child_local_surface_id);
+
+  test::Quad fallback_child_quads[] = {test::Quad::SolidColorQuad(SK_ColorRED)};
+  test::Pass fallback_child_passes[] = {
+      test::Pass(fallback_child_quads, arraysize(fallback_child_quads))};
+
+  // Submit a CompositorFrame to the fallback Surface containing a red
+  // SolidColorDrawQuad.
+  SubmitCompositorFrame(&fallback_child_factory, fallback_child_passes,
+                        arraysize(fallback_child_passes),
+                        fallback_child_local_surface_id);
+
+  // Try to embed |primary_child_surface_id| and if unavailabe, embed
+  // |fallback_child_surface_id|.
+  test::Quad root_quads[] = {test::Quad::SurfaceQuad(
+      primary_child_surface_id, fallback_child_surface_id, 1.f)};
+  test::Pass root_passes[] = {test::Pass(root_quads, arraysize(root_quads))};
+
+  SubmitCompositorFrame(&factory_, root_passes, arraysize(root_passes),
+                        root_local_surface_id_);
+
+  // The CompositorFrame is submitted to |primary_child_surface_id|, so
+  // |fallback_child_surface_id| will not be used and we should see a green
+  // SolidColorDrawQuad.
+  test::Quad expected_quads1[] = {test::Quad::SolidColorQuad(SK_ColorGREEN)};
+  test::Pass expected_passes1[] = {
+      test::Pass(expected_quads1, arraysize(expected_quads1))};
+
+  SurfaceId root_surface_id(factory_.frame_sink_id(), root_local_surface_id_);
+  SurfaceId ids[] = {root_surface_id, primary_child_surface_id,
+                     fallback_child_surface_id};
+  AggregateAndVerify(expected_passes1, arraysize(expected_passes1), ids,
+                     arraysize(ids));
+
+  primary_child_factory.EvictSurface();
+  fallback_child_factory.EvictSurface();
+}
+
 TEST_F(SurfaceAggregatorValidSurfaceTest, CopyRequest) {
   SurfaceFactory embedded_factory(kArbitraryChildFrameSinkId1, &manager_,
                                   &empty_client_);