Previously, nested components (that are never standalone) were making
their own requests for comments, creating unecessary duplicate API
requests.
Some requests were made to the rest API directly (for example,
gr-change-view requested comments this way), and some were through the
gr-comment-api, which also helped handle comment manipulation and
reorganization.
Instead of ad-hoc comment requesting, move all comment requests to the
top level (standalone) component, and use an object prototype to
generate _changeComments as a property on gr-comment-api. This is an
immutable object that can be passed to the inner components
(file list, etc), and includes the methods needed to manipulate
comments into the forms
necessary.
When a child component needs to trigger a refresh of the comments, fire
an event that the parent event handles (see gr-file-list l.867).
Bug: Issue 6953
Change-Id: Ic4b6cf16520baae65d8cf956c311a60f2a70a2e1
