Support ozone=1 compositor_unittests with OSMesa

ui/gl/gl_context_ozone.cc

Index: ui/gl/gl_context_ozone.cc
diff --git a/ui/gl/gl_context_ozone.cc b/ui/gl/gl_context_ozone.cc
index aeb91953df78b50bdf34af22cb8ced2d5494d8f1..058bb387e88aba238112ed85fd23006c495b8277 100644
--- a/ui/gl/gl_context_ozone.cc
+++ b/ui/gl/gl_context_ozone.cc
@@ -9,6 +9,7 @@
 #include "base/sys_info.h"
 #include "ui/gl/gl_bindings.h"
 #include "ui/gl/gl_context_egl.h"
+#include "ui/gl/gl_context_osmesa.h"
 #include "ui/gl/gl_context_stub.h"
 #include "ui/gl/gl_implementation.h"
 #include "ui/gl/gl_surface.h"
@@ -23,6 +24,13 @@ scoped_refptr<GLContext> GLContext::CreateGLContext(
   if (GetGLImplementation() == kGLImplementationMockGL)
     return scoped_refptr<GLContext>(new GLContextStub());
 
+  if (GetGLImplementation() == kGLImplementationOSMesaGL) {
+    scoped_refptr<GLContext> context(new GLContextOSMesa(share_group));
+    if (!context->Initialize(compatible_surface, gpu_preference))
+      return NULL;
+    return context;
+  }
+
   scoped_refptr<GLContext> context;
   if (!compatible_surface->GetHandle()) {
     DLOG(ERROR) << "Surface has no associated handle.\n";