snippet: Move the hook to be a property of the snippet

Instead of specifying the hook point when adding to the pipeline using
a separate function for each hook, the hook is now a property of the
snippet. The hook is set on construction and is then read-only.

Reviewed-by: Robert Bragg <robert@linux.intel.com>

cogl/cogl-snippet.c

@@ -38,19 +38,30 @@ _cogl_snippet_free (CoglSnippet *snippet);
 COGL_OBJECT_DEFINE (Snippet, snippet);
 
 CoglSnippet *
-cogl_snippet_new (const char *declarations,
+cogl_snippet_new (CoglSnippetHook hook,
+                  const char *declarations,
                   const char *post)
 {
   CoglSnippet *snippet = g_slice_new0 (CoglSnippet);
 
   _cogl_snippet_object_new (snippet);
 
+  snippet->hook = hook;
+
   cogl_snippet_set_declarations (snippet, declarations);
   cogl_snippet_set_post (snippet, post);
 
   return snippet;
 }
 
+CoglSnippetHook
+cogl_snippet_get_hook (CoglSnippet *snippet)
+{
+  _COGL_RETURN_VAL_IF_FAIL (cogl_is_snippet (snippet), 0);
+
+  return snippet->hook;
+}
+
 static gboolean
 _cogl_snippet_modify (CoglSnippet *snippet)
 {