Forward --password-store switch to os_crypt

Forward --password-store switch to os_crypt

Password manager uses a switch to allow the user to override the
auto-detection of the appropriate password store. OSCrypt should
respect this switch as well.

The switch value is read and passed to OSCrypt at a very early
point in Chrome's start, before any of OSCrypt's dependents
use it.

I also reworked OSCrypt's build to make it simpler for chrome to
deduce whether the linux implementation of OSCrypt will be used.
 - Previously, os_crypt_linux was used only if we also decided to
   link at least one linux backend. Otherwise we used os_crypt_posix.
 + Now, we always use the linux implementation for linux. If no
   KeyStorage is linked, the linux implementation defaults to the
   same behavior as for posix.

This CL is a fixed version of https://codereview.chromium.org/2118443002/

Note: old BUG was 602624, but the merge approval is at 643189.
BUG=643189
Review-Url: https://codereview.chromium.org/2159743002
Cr-Commit-Position: refs/heads/master@{#406056}
(cherry picked from commit 3ea4c69178fd68bcdc880bc2c83481e57e293403)

Committed: https://chromium.googlesource.com/chromium/src/+/1673c9e4ac994c620bc08a7ee9cd963515a26fb4

[vabr (Chromium), 2016-09-06 08:47:29]

Description was changed from

==========
Forward --password-store switch to os_crypt

Password manager uses a switch to allow the user to override the
auto-detection of the appropriate password store. OSCrypt should
respect this switch as well.

The switch value is read and passed to OSCrypt at a very early
point in Chrome's start, before any of OSCrypt's dependents
use it.

I also reworked OSCrypt's build to make it simpler for chrome to
deduce whether the linux implementation of OSCrypt will be used.
 - Previously, os_crypt_linux was used only if we also decided to
   link at least one linux backend. Otherwise we used os_crypt_posix.
 + Now, we always use the linux implementation for linux. If no
   KeyStorage is linked, the linux implementation defaults to the
   same behavior as for posix.

This CL is a fixed version of https://codereview.chromium.org/2118443002/

Note: old BUG was 602624, but the merge approval is at 643189.
BUG=643189

Review-Url: https://codereview.chromium.org/2159743002
Cr-Commit-Position: refs/heads/master@{#406056}
(cherry picked from commit 3ea4c69178fd68bcdc880bc2c83481e57e293403)
==========

to

==========
Forward --password-store switch to os_crypt

Password manager uses a switch to allow the user to override the
auto-detection of the appropriate password store. OSCrypt should
respect this switch as well.

The switch value is read and passed to OSCrypt at a very early
point in Chrome's start, before any of OSCrypt's dependents
use it.

I also reworked OSCrypt's build to make it simpler for chrome to
deduce whether the linux implementation of OSCrypt will be used.
 - Previously, os_crypt_linux was used only if we also decided to
   link at least one linux backend. Otherwise we used os_crypt_posix.
 + Now, we always use the linux implementation for linux. If no
   KeyStorage is linked, the linux implementation defaults to the
   same behavior as for posix.

This CL is a fixed version of https://codereview.chromium.org/2118443002/

Note: old BUG was 602624, but the merge approval is at 643189.
BUG=643189

Review-Url: https://codereview.chromium.org/2159743002
Cr-Commit-Position: refs/heads/master@{#406056}
(cherry picked from commit 3ea4c69178fd68bcdc880bc2c83481e57e293403)

Committed:
https://chromium.googlesource.com/chromium/src/+/1673c9e4ac994c620bc08a7ee9cd...
==========

[vabr (Chromium), 2016-09-06 08:47:30]

Committed patchset #1 (id:1) manually as
1673c9e4ac994c620bc08a7ee9cd963515a26fb4.