Add a full Blimp integration test.

blimp/client/test/compositor/BUILD.gn

 # 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.
 
-group("support") {
+source_set("compositor") {
+  testonly = true
+
+  sources = [
+    "mock_compositor_dependencies.cc",
+    "mock_compositor_dependencies.h",
+    "test_display_compositor.cc",
+    "test_display_compositor.h",
+  ]
+
+  deps = [
+    "//cc:test_support",
+  ]
+
   public_deps = [
     "//blimp/client/support/compositor",
   ]
 }
-
-group("test_support") {
-  testonly = true
-
-  public_deps = [
-    "//blimp/client/support/compositor:test_support",
-  ]
-}