add support for GL_EXT_debug_marker

This extension is always added to the GL_EXTENSIONS
extension string for the current GL context, regardless
of if it's supported by the h/w driver.

The extension itself will be handled by GLES_trace (eventually),
when GLES_trace is not enabled, it'll result to a no-op.

If the h/w implementation has this extension, we'll call that version
instead of our dummy version.

Change-Id: Ie5dd3387c4d45cd5ed5f03b73bda6045620a96bc
diff --git a/opengl/libs/EGL/egl.cpp b/opengl/libs/EGL/egl.cpp
index e053589..83933e5 100644
--- a/opengl/libs/EGL/egl.cpp
+++ b/opengl/libs/EGL/egl.cpp
@@ -233,6 +233,26 @@
 
 // ----------------------------------------------------------------------------
 
+const GLubyte * egl_get_string_for_current_context(GLenum name) {
+    // NOTE: returning NULL here will fall-back to the default
+    // implementation.
+
+    EGLContext context = egl_tls_t::getContext();
+    if (context == EGL_NO_CONTEXT)
+        return NULL;
+
+    egl_context_t const * const c = get_context(context);
+    if (c == NULL) // this should never happen, by construction
+        return NULL;
+
+    if (name != GL_EXTENSIONS)
+        return NULL;
+
+    return (const GLubyte *)c->gl_extensions.string();
+}
+
+// ----------------------------------------------------------------------------
+
 // this mutex protects:
 //    d->disp[]
 //    egl_init_drivers_locked()
@@ -290,6 +310,9 @@
     ALOGE("called unimplemented OpenGL ES API");
 }
 
+void gl_noop() {
+}
+
 // ----------------------------------------------------------------------------
 
 #if USE_FAST_TLS_KEY