[Extensions] Make a chrome.developerPrivate.getExtensionsInfo function
Make a new function, developerPrivate.getExtensionsInfo,
to handle generating and returning info about installed
extensions. We do this, instead of adjusting the current
(developerPrivate.getItemsInfo) to allow for breaking
changes - which lets us have consistent style and fewer
parameters.
BUG=
461039
Committed: 
https://crrev.com/609f7a872624668960c7da22221924c47a8f885f
Cr-Commit-Position: refs/heads/master@{#320355}