The main content block has no contextual links. I believe this is related to _block_get_renderable_array but I'm not really sure. I'm using Custom Contextual Links module to add contextual links to blocks, but of course it doesn't work with system-main (the main content block).
Contextual module (core) will preprocess the block renderable array and turn
While block module relies on _block_get_renderable_array for performance reasons, contextual links example module (from the examples package) shows an example of setting
As for CCL, it relies on hook_contextual_links_view_alter which will only alter or add links if there is already a
This answer is not related to user's question. I wrote this in case others similar like me is looking for adding contextual link in hook_block_view.
Here is the contextual link example module mentioned by Barraponto regarding setting #contextual_links on hook_block_view.
Another example will be the original drupal menu module.
Hope it helps other who facing similar problem like me.