desktop-pwas: Skeleton for BookmarkAppInstallationTask

Introduces the BookmarkAppInstallationTask. This class purpose is to
perform the necessary steps to install an BookmarkApp from a
WebContents or a WebApplicationInfo.

This class will have two subclasses BookmarkAppShortcutInstallation task
and BookmarkAppWebAppInstallationTask. The former is included in this
CL and installs BookmarkApp-based Shortcuts. The latter will install
BookmarkApp-based Web Apps.

Bug: 864904

Change-Id: I5b5b9f44ff0984b0138663cb7c84abcba1062c77
Reviewed-on: https://chromium-review.googlesource.com/1131024
Commit-Queue: Giovanni Ortuño Urquidi <ortuno@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Dominick Ng <dominickn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#577790}
13 files changed