Add OzoneGLImpl interface.

ui/gl/init/ozone_util.h

Index: ui/gl/init/ozone_util.h
diff --git a/ui/gl/init/ozone_util.h b/ui/gl/init/ozone_util.h
new file mode 100644
index 0000000000000000000000000000000000000000..268daa93d5d6f8d1b7d42a744b6dcb2d49fd523c
--- /dev/null
+++ b/ui/gl/init/ozone_util.h
@@ -0,0 +1,43 @@
+// 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.
+
+#ifndef UI_GL_INIT_OZONE_UTIL_H_
+#define UI_GL_INIT_OZONE_UTIL_H_
+
+#include "base/macros.h"
+#include "ui/gl/gl_implementation.h"
+#include "ui/ozone/public/gl_ozone.h"
+#include "ui/ozone/public/ozone_platform.h"
+#include "ui/ozone/public/surface_factory_ozone.h"
+
+namespace gl {
+
+inline ui::SurfaceFactoryOzone* GetSurfaceFactory() {

[piman, 2016/08/31 20:05:09]

nit: gl::GetSurfaceFactory doesn't make it clear that it's specific to Ozone.
Could we make it GetOzoneSurfaceFactory, or gl::ozone::GetSurfaceFactory, or
something?

[kylechar, 2016/09/01 13:57:21]

Done.

+  return ui::OzonePlatform::GetInstance()->GetSurfaceFactoryOzone();
+}
+
+// Returns true if there is an GLOzone for the specified GL implementation.
+inline bool HasGLOzone(GLImplementation impl) {
+  return GetSurfaceFactory()->GetGLOzone(impl) != nullptr;

[piman, 2016/08/31 20:05:09]

Is the plan to have this always be true? If not, could we make a default one,
and move all the logic in gl_factory_ozone and gl_initializer_ozone that depends
on !HasGLOzone to that default GLOzone?

[kylechar, 2016/09/01 13:57:21]

I think that yes, it would always be true. I could add a different way to check
if a GLOzone exists for the GLImplementation but it seems unnecessary (more
boilerplate to write for each Ozone platform). Also, for example, if
impl=kGLImplementationAppleGL then you probably don't want to return a default
because something is super wrong.

Although you're absolutely right I could move the osmesa and mock GL code into
GLOzoneOsmesa and GLOzoneMock respectively. That way each of the functions in
gl_ozone_initializer/gl_ozone_factory would look like:

bool InitializeGLOneOffPlatform() {
  return GetGLOzone()->InitializeGLOneOffPlatform();
}

That would be a nice change.

[piman, 2016/09/01 17:43:04]

Right, I would like that in the end state we don't have half of the logic in
ui/gl/init and the other half in ui/ozone - it's harder to follow and to
maintain.

+}
+
+// Returns true if there is an GLOzone for the set GL implementation.
+inline bool HasGLOzone() {
+  return HasGLOzone(GetGLImplementation());
+}
+
+// Returns the GLOzone for the specified GL implementation or null if none
+// exists.
+inline ui::GLOzone* GetGLOzone(GLImplementation impl) {
+  return GetSurfaceFactory()->GetGLOzone(impl);
+}
+
+// Returns the GLOzone for the set GL implementation or null if none exists.
+inline ui::GLOzone* GetGLOzone() {
+  return GetGLOzone(GetGLImplementation());
+}
+
+}  // namespace gl
+
+#endif  // UI_GL_INIT_OZONE_UTIL_H_