Add missing ScopedAllowBlocking to TabManagerDelegateChromeos.

TabManagerDelegateChromeos reads the "low memory margin" and "available"
memory values from kernel-provided entries in the filesystem, when
determining how many processes need to be discarded to ease memory
pressure. This causes AssertIOAllowed to fail if discards ever trigger
in a build with DCHECKs enabled.

In principle the reads from these kernel-provided files should not block
so add a ScopedAllowBlocking to work-around the issue.

Bug: 
Change-Id: I472f7fca8a4780e6a6abceb0a3baff541c8e3a9b
Reviewed-on: https://chromium-review.googlesource.com/738224
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Cheng-Yu Lee <cylee@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#511951}

CrOS-Libchrome-Original-Commit: 06af95868491b8ea0f45bb442c97f0f8299ebbb0
1 file changed
tree: 4133b056bbccb0b2ccaa6c9555b66be8a1b16011
  1. base/
  2. build/
  3. components/
  4. dbus/
  5. device/
  6. ipc/
  7. mojo/
  8. testing/
  9. third_party/
  10. ui/