chromeos: fix id sent to parent in OnFrameSinkIdAllocated()

It was passing in the FrameSinkId, when it should have passed in the window
id.

BUG=837686
TEST=covered by test

Change-Id: I2f6920528403452696d358110605aa85519a0b2d
Reviewed-on: https://chromium-review.googlesource.com/1110748Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569391}

services/ui/ws2/window_tree.cc

@@ -763,11 +763,9 @@ bool WindowTree::EmbedImpl(const ClientWindowId& window_id,
   if (flags & mojom::kEmbedFlagEmbedderControlsVisibility)
     embedding->embedded_tree()->can_change_root_window_visibility_ = false;
   ServerWindow* server_window = ServerWindow::GetMayBeNull(window);
-  const ClientWindowId client_window_id = server_window->frame_sink_id();
   server_window->SetEmbedding(std::move(embedding));
   window_tree_client_->OnFrameSinkIdAllocated(
-      ClientWindowIdToTransportId(client_window_id),
-      server_window->frame_sink_id());
+      ClientWindowIdToTransportId(window_id), server_window->frame_sink_id());
   return true;
 }
 

services/ui/ws2/window_tree_unittest.cc

@@ -1005,6 +1005,11 @@ TEST(WindowTreeTest2, Embed) {
   // OnFrameSinkIdAllocated() should called on the parent tree.
   ASSERT_EQ(1u, setup.changes()->size());
   EXPECT_EQ(CHANGE_TYPE_FRAME_SINK_ID_ALLOCATED, (*setup.changes())[0].type);
+  const Id embed_window_transport_id =
+      setup.window_tree_test_helper()->TransportIdForWindow(embed_window);
+  EXPECT_EQ(embed_window_transport_id, (*setup.changes())[0].window_id);
+  EXPECT_EQ(ServerWindow::GetMayBeNull(embed_window)->frame_sink_id(),
+            (*setup.changes())[0].frame_sink_id);
 }
 
 // Base class for ScheduleEmbed() related tests. This creates a Window and