aura: Clean up compositor initialization/destruction.

ui/aura/test/aura_test_helper.cc

Index: ui/aura/test/aura_test_helper.cc
diff --git a/ui/aura/test/aura_test_helper.cc b/ui/aura/test/aura_test_helper.cc
index b1801903c809e3a7868f42e2acf610f31913eb07..0bcc515a637d73958deaad6059917d3349fab282 100644
--- a/ui/aura/test/aura_test_helper.cc
+++ b/ui/aura/test/aura_test_helper.cc
@@ -16,6 +16,7 @@
 #include "ui/aura/test/test_screen.h"
 #include "ui/aura/test/test_stacking_client.h"
 #include "ui/base/ime/dummy_input_method.h"
+#include "ui/compositor/compositor.h"
 #include "ui/compositor/layer_animator.h"
 #include "ui/compositor/scoped_animation_duration_scale_mode.h"
 #include "ui/gfx/screen.h"
@@ -59,6 +60,11 @@ AuraTestHelper::~AuraTestHelper() {
 
 void AuraTestHelper::SetUp() {
   setup_called_ = true;
+
+  // The ContextFactory must exist before any Compositors are created.
+  bool allow_test_contexts = true;
+  ui::Compositor::InitializeContextFactoryForTests(allow_test_contexts);
+
   Env::GetInstance();
   test_screen_.reset(TestScreen::Create());
   gfx::Screen::SetScreenInstance(gfx::SCREEN_TYPE_NATIVE, test_screen_.get());