aura: Clean up compositor initialization/destruction.

ui/compositor/compositor.h

Index: ui/compositor/compositor.h
diff --git a/ui/compositor/compositor.h b/ui/compositor/compositor.h
index c8689b179b2ce914ebbc283fa1e69f7360e9b618..92cdd7194f80c7991e9b5c60e8d796ad8934a0f5 100644
--- a/ui/compositor/compositor.h
+++ b/ui/compositor/compositor.h
@@ -99,6 +99,10 @@ class COMPOSITOR_EXPORT ContextFactory {
 
   // Destroys per-compositor data.
   virtual void RemoveCompositor(Compositor* compositor) = 0;
+
+  // When true, the factory uses test contexts that do not do real GL
+  // operations.
+  virtual bool DoesCreateTestContexts() = 0;
 };
 
 // The default factory that creates in-process contexts.
@@ -123,6 +127,7 @@ class COMPOSITOR_EXPORT DefaultContextFactory : public ContextFactory {
   virtual scoped_refptr<cc::ContextProvider>
       OffscreenContextProviderForCompositorThread() OVERRIDE;
   virtual void RemoveCompositor(Compositor* compositor) OVERRIDE;
+  virtual bool DoesCreateTestContexts() OVERRIDE;
 
   bool Initialize();
 
@@ -161,6 +166,7 @@ class COMPOSITOR_EXPORT TestContextFactory : public ContextFactory {
   virtual scoped_refptr<cc::ContextProvider>
       OffscreenContextProviderForCompositorThread() OVERRIDE;
   virtual void RemoveCompositor(Compositor* compositor) OVERRIDE;
+  virtual bool DoesCreateTestContexts() OVERRIDE;
 
  private:
   scoped_refptr<ContextProviderFromContextFactory>
@@ -290,6 +296,14 @@ class COMPOSITOR_EXPORT Compositor
              gfx::AcceleratedWidget widget);
   virtual ~Compositor();
 
+  // Set up the compositor ContextFactory for a test environment. Unit tests
+  // that do not have a full content environment need to call this before
+  // initializing the Compositor.
+  // Some tests expect pixel output, and they should pass false for
+  // |allow_test_contexts|. Most unit tests should pass true. Once this has been
+  // called, the Initialize() and Terminate() methods should be used as normal.
+  static void InitializeContextFactoryForTests(bool allow_test_contexts);
+
   static void Initialize();
   static bool WasInitializedWithThread();
   static scoped_refptr<base::MessageLoopProxy> GetCompositorMessageLoop();