exo: Add support for subcompositor interface.

components/exo/display_unittest.cc

Index: components/exo/display_unittest.cc
diff --git a/components/exo/display_unittest.cc b/components/exo/display_unittest.cc
index 827452942f8920f2de70dfc9e648fc008dadb129..0f70d0ed393ffcea38fb5e7a54e6e2d64e9858fc 100644
--- a/components/exo/display_unittest.cc
+++ b/components/exo/display_unittest.cc
@@ -6,6 +6,7 @@
 #include "components/exo/display.h"
 #include "components/exo/shared_memory.h"
 #include "components/exo/shell_surface.h"
+#include "components/exo/sub_surface.h"
 #include "components/exo/surface.h"
 #include "components/exo/test/exo_test_base.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -63,5 +64,23 @@ TEST_F(DisplayTest, CreateShellSurface) {
       display->CreateShellSurface(surface2.get());
 }
 
+TEST_F(DisplayTest, CreateSubSurface) {
+  scoped_ptr<Display> display(new Display);
+
+  // Create two surfaces.
+  scoped_ptr<Surface> surface1 = display->CreateSurface();
+  EXPECT_TRUE(surface1);
+  scoped_ptr<Surface> surface2 = display->CreateSurface();
+  EXPECT_TRUE(surface2);
+
+  // Create a shell surface for surface1.
+  scoped_ptr<ShellSurface> shell_surface1 =
+      display->CreateShellSurface(surface1.get());
+
+  // Create a sub surface for surface2.
+  scoped_ptr<SubSurface> sub_surface1 =
+      display->CreateSubSurface(surface2.get(), surface1.get());
+}
+
 }  // namespace
 }  // namespace exo