Discard compositor frames from unloaded web content

cc/trees/layer_tree_host_unittest.cc

 // Copyright 2011 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 "cc/trees/layer_tree_host.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 6992 matching lines @@
     EXPECT_EQ(21u, frame.resource_list.size());
 
     EndTest();
   }
 
   void AfterTest() override {}
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostTestSubmitFrameResources);
 
+// Ensure that content_source_id is propagated to the frame's metadata.
+class LayerTreeHostTestContentSourceId : public LayerTreeHostTest {
+ protected:
+  void BeginTest() override {
+    layer_tree_host()->SetContentSourceId(5);
+    PostSetNeedsCommitToMainThread();
+  }
+
+  DrawResult PrepareToDrawOnThread(LayerTreeHostImpl* host_impl,
+                                   LayerTreeHostImpl::FrameData* frame_data,
+                                   DrawResult draw_result) override {
+    EXPECT_EQ(DRAW_SUCCESS, draw_result);
+    EXPECT_EQ(5U, host_impl->active_tree()->content_source_id());
+    return draw_result;
+  }
+
+  void DisplayReceivedCompositorFrameOnThread(
+      const CompositorFrame& frame) override {
+    EXPECT_EQ(5U, frame.metadata.content_source_id);
+    EndTest();
+  }
+
+  void AfterTest() override {}
+};
+
+SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostTestContentSourceId);
+
 }  // namespace
 }  // namespace cc