Merge branch 'js-content-for' into 'master'

Re-implement page-specific JS in a better way.

## What does this MR do?

This rebuilds the way we do page-specific JavaScript assets for a few reasons:

- The current implementation does not work with Subresource Integrity (!4808)
- The current implementation doesn't allow caching of libraries because each page we hook up with this system will have a separate application.js. Meaning that for every page that uses Ace Editor, we'd have to load Ace Editor plus any GitLab-specific scripts in the same file, making local caching of just Ace Editor impossible.
- The current implementation is rather hacky.

## Are there points in the code the reviewer needs to double check?

That Sprockets doesn't choke on this when we use precompiled assets.

## What are the relevant issue numbers?

#14372

## Does this MR meet the acceptance criteria?

- [x] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
- [x] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [x] API support added
- Tests
  - [x] Added for this feature/bug
  - [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
- [x] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

cc: @jschatz1 @pavelloz

Thanks to @pavelloz for his example implementation which was very useful.

See merge request !4883

2 files changed, 6 insertions, 2 deletions

diff --git a/app/views/projects/graphs/_head.html.haml b/app/views/projects/graphs/_head.html.haml
index a388d9a0a61..ca347406dfe 100644
--- a/app/views/projects/graphs/_head.html.haml
+++ b/app/views/projects/graphs/_head.html.haml
@@ -1,7 +1,9 @@
 .nav-links.sub-nav
   %ul{ class: (container_class) }
 
-    - page_specific_javascripts asset_path("graphs/application.js")
+    - content_for :page_specific_javascripts do
+      = page_specific_javascript_tag('lib/chart.js')
+      = page_specific_javascript_tag('graphs/application.js')
     = nav_link(action: :show) do
       = link_to 'Contributors', namespace_project_graph_path
     = nav_link(action: :commits) do
diff --git a/app/views/projects/network/show.html.haml b/app/views/projects/network/show.html.haml
index 593af319a47..3ca30b4ba6b 100644
--- a/app/views/projects/network/show.html.haml
+++ b/app/views/projects/network/show.html.haml
@@ -1,5 +1,7 @@
 - page_title "Network", @ref
-- page_specific_javascripts asset_path("network/application.js")
+- content_for :page_specific_javascripts do
+  = page_specific_javascript_tag('lib/raphael.js')
+  = page_specific_javascript_tag('network/application.js')
 = render "projects/commits/head"
 = render "head"
 %div{ class: (container_class) }