Move SkGLContext and some GrGLInterface implementations to skgputest module

tools/gpu/gl/null/NullGLContext.h

Index: tools/gpu/gl/null/NullGLContext.h
diff --git a/tools/gpu/gl/null/NullGLContext.h b/tools/gpu/gl/null/NullGLContext.h
new file mode 100644
index 0000000000000000000000000000000000000000..16fb9fd1df8b0d776fef6cbacbe5dc158260e676
--- /dev/null
+++ b/tools/gpu/gl/null/NullGLContext.h
@@ -0,0 +1,17 @@
+
+/*
+ * Copyright 2011 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef NullGLContext_DEFINED
+#define NullGLContext_DEFINED
+
+#include "gl/GLContext.h"
+
+namespace sk_gpu_test {
+GLContext* CreateNullGLContext();
+}  // namespace sk_gpu_test
+
+#endif