Determine whether to show "Add to Homescreen" dialog or WebAPK infobar
This CL:
- Introduces a new class, AddToHomescreenProcess, which manages the
add-to-homescreen process. AddToHomescreenProcess is largely copied from
AddToHomescreenDialogHelper
- The CL adds logic to AddToHomescreenProcess to determine whether to show
the add-WebAPK-to-homescreen infobar instead of the add-to-homescreen dialog.
- Changes the entry point for adding a page to the homescreen from
AddToHomescreenDialog#show() to AddToHomescreenProcess#start()
BUG=
627250,
606430,
635933