The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ee088c9f11822f91a180217765a1f71261e24038

commit ee088c9f11822f91a180217765a1f71261e24038
Author: dominickn <dominickn@chromium.org>
Date: Tue Jun 27 08:02:50 2017

Don't block InstallableManager::GetData calls when waiting for a service worker.

If the InstallableManager is processing a task that is waiting for the
site to register a service worker, all new tasks will block until the
first task is complete. If the site never registers a service worker,
all new calls to InstallableManager will never succeed, even if they are
not requesting a service worker check.

This is particularly important if installability checking on page load is
enabled. Trying to add a non-PWA with a manifest and icon to
homescreen will not use the manifest icon or details since the onload
check is hanging waiting for a service worker.

This CL addresses the bug by introducing a paused task queue to hold
waiting tasks. Existing tests are amended to explicitly check the paused
case.

BUG= 737013 

Review-Url: https://codereview.chromium.org/2963473003
Cr-Commit-Position: refs/heads/master@{#482564}

[modify] https://crrev.com/ee088c9f11822f91a180217765a1f71261e24038/chrome/browser/installable/installable_manager.cc
[modify] https://crrev.com/ee088c9f11822f91a180217765a1f71261e24038/chrome/browser/installable/installable_manager.h
[modify] https://crrev.com/ee088c9f11822f91a180217765a1f71261e24038/chrome/browser/installable/installable_manager_browsertest.cc