Preserve FrameSinkSourceMapping nodes that have path to root

cc/surfaces/surface_manager_unittest.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stddef.h>
 
 #include "cc/scheduler/begin_frame_source.h"
 #include "cc/surfaces/surface_factory_client.h"
 #include "cc/surfaces/surface_manager.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 163 matching lines @@
 
   // Cleanup hierarchy.
   manager_.UnregisterFrameSinkHierarchy(root2.frame_sink_id(),
                                         client_c.frame_sink_id());
   manager_.UnregisterFrameSinkHierarchy(client_c.frame_sink_id(),
                                         client_a.frame_sink_id());
   manager_.UnregisterFrameSinkHierarchy(client_a.frame_sink_id(),
                                         client_b.frame_sink_id());
 }
 
+// This test verifies that a BeginFrameSource path to the root from a
+// FrameSinkId is preserved even if that FrameSinkId has no children
+// and does not have a corresponding SurfaceFactoryClient.
+TEST_F(SurfaceManagerTest, ParentWithoutClientRetained) {
+  StubBeginFrameSource root_source;
+
+  constexpr FrameSinkId kFrameSinkIdRoot(1, 1);
+  constexpr FrameSinkId kFrameSinkIdA(2, 2);
+  constexpr FrameSinkId kFrameSinkIdB(3, 3);
+  constexpr FrameSinkId kFrameSinkIdC(4, 4);
+
+  FakeSurfaceFactoryClient root(kFrameSinkIdRoot, &manager_);
+  FakeSurfaceFactoryClient client_b(kFrameSinkIdB, &manager_);
+  FakeSurfaceFactoryClient client_c(kFrameSinkIdC, &manager_);
+
+  manager_.RegisterBeginFrameSource(&root_source, root.frame_sink_id());
+  EXPECT_EQ(&root_source, root.source());
+
+  // Set up initial hierarchy: root -> A -> B.
+  // Note that A does not have a SurfaceFactoryClient.
+  manager_.RegisterFrameSinkHierarchy(kFrameSinkIdRoot, kFrameSinkIdA);
+  manager_.RegisterFrameSinkHierarchy(kFrameSinkIdA, kFrameSinkIdB);
+  // The root's BeginFrameSource should propagate to B.
+  EXPECT_EQ(root.source(), client_b.source());
+
+  // Unregister B, and attach C to A: root -> A -> C
+  manager_.UnregisterFrameSinkHierarchy(kFrameSinkIdA, kFrameSinkIdB);
+  EXPECT_EQ(nullptr, client_b.source());
+  manager_.RegisterFrameSinkHierarchy(kFrameSinkIdA, kFrameSinkIdC);
+  // The root's BeginFrameSource should propagate to C.
+  EXPECT_EQ(root.source(), client_c.source());
+
+  manager_.UnregisterBeginFrameSource(&root_source);
+  EXPECT_EQ(nullptr, root.source());
+  EXPECT_EQ(nullptr, client_c.source());
+}
+
 // In practice, registering and unregistering both parent/child relationships
 // and SurfaceFactoryClients can happen in any ordering with respect to
 // each other.  These following tests verify that all the data structures
 // are properly set up and cleaned up under the four permutations of orderings
 // of this nesting.
 
 class SurfaceManagerOrderingTest : public SurfaceManagerTest {
  public:
   SurfaceManagerOrderingTest()
       : client_a_(FrameSinkId(1, 1)),
@@ skipping 172 matching lines @@
 }
 
 INSTANTIATE_TEST_CASE_P(
     SurfaceManagerOrderingParamTestInstantiation,
     SurfaceManagerOrderingParamTest,
     ::testing::Combine(::testing::ValuesIn(kRegisterOrderList),
                        ::testing::ValuesIn(kUnregisterOrderList),
                        ::testing::ValuesIn(kBFSOrderList)));
 
 }  // namespace cc