Refactor GL bindings so there is no global GLApi or DriverGL.

ui/gl/init/gl_factory_mac.cc

Index: ui/gl/init/gl_factory_mac.cc
diff --git a/ui/gl/init/gl_factory_mac.cc b/ui/gl/init/gl_factory_mac.cc
index 1bcfbadd2e42d337b5e3201e8a2f9f4517eddc73..fce7f2e159680b5769d05a762db6da3a82cd97f8 100644
--- a/ui/gl/init/gl_factory_mac.cc
+++ b/ui/gl/init/gl_factory_mac.cc
@@ -87,6 +87,12 @@ scoped_refptr<GLContext> CreateGLContext(GLShareGroup* share_group,
                                  compatible_surface, attribs);
     case kGLImplementationMockGL:
       return new GLContextStub(share_group);
+    case kGLImplementationStubGL: {
+      scoped_refptr<GLContextStub> stub_context =
+          new GLContextStub(share_group);
+      stub_context->SetUseStubApi(true);
+      return stub_context;
+    }
     default:
       NOTREACHED();
       return nullptr;
@@ -106,6 +112,7 @@ scoped_refptr<GLSurface> CreateViewGLSurface(gfx::AcceleratedWidget window) {
       return InitializeGLSurface(new GLSurfaceOSMesaHeadless());
     }
     case kGLImplementationMockGL:
+    case kGLImplementationStubGL:
       return new GLSurfaceStub;
     default:
       NOTREACHED();
@@ -127,6 +134,7 @@ scoped_refptr<GLSurface> CreateOffscreenGLSurfaceWithFormat(
       return InitializeGLSurfaceWithFormat(
           new NoOpGLSurface(size), format);
     case kGLImplementationMockGL:
+    case kGLImplementationStubGL:
       return new GLSurfaceStub;
     default:
       NOTREACHED();