Implement "content type" callback for "block" content type

On my development site, the following takes 2.5 seconds:

foreach (module_list() as $module) {
  module_invoke($module, 'block', 'list');
}

By far the most expensive function is views_block(). It exposes each defined view as a block. My site has more 500+ views defined. These are not manually defined views. AFAICT most views are exported by the Nodequeue module in nodequeue_views_default_views(). I don't use any of these views as a block.

My 100+ mini panels are also exposed as blocks. In total, more than 900 blocks are returned by the above code.

With my patch we only invoke hook_block() on modules whose blocks I actually use and not others. This saves me a call to views_block() and the corresponding 500+ calls to panels_default_block_info() for each of the blocks returned by that function. On my development machine, the patch cuts about 2 seconds off the page generation time for pages using the block content type.

Is that compelling enough? :-)

I know that this is a complex site with a lot of modules, views, mini panels etc. But even on a smaller scale there may be a measurable saving, especially with modules like Views that expose a lot of blocks based on other data sources.