Updates SQL code now that mmap is supported on iOS.

Updates SQL code now that mmap is supported on iOS.

BUG=621065
TEST=None

Committed: https://crrev.com/83d6b83a933f827466509945ad1ca68f0053fd93
Cr-Commit-Position: refs/heads/master@{#400915}

[rohitrao (ping after 24h), 2016-06-20 14:07:07]

rohitrao@chromium.org changed reviewers:
+ shess@chromium.org

[rohitrao (ping after 24h), 2016-06-20 14:07:07]

Different versions of iOS now have different mmap behaviors, which means that we
have to use runtime checks instead of compile-time checks.  This makes the tests
a bit more convoluted than before, but hopefully not too terrible.

[rohitrao (ping after 24h), 2016-06-20 14:07:42]

Description was changed from

==========
Updates SQL code now that mmap is supported on iOS.

BUG=621065
TEST=None
==========

to

==========
Updates SQL code now that mmap is supported on iOS.

BUG=621065
TEST=None
==========

[Scott Hess - ex-Googler, 2016-06-20 17:59:25]

LGTM, with one concern.

My concern is whether there are both OS-version interactions and SDK-version
interactions.  Like could SDK-version cause an older SQLite version to be used
which may have latent bugs in mmap support?  I am not aware of any such bugs,
but I don't really keep close track of SQLite changes outside the specific
releases pulled into Chromium's tree, and anyhow Apple may have their own
patches in there.

If running iOS version forces SQLite version, that addresses my concerns.  My
assumption is that that's how things work.

[rohitrao (ping after 24h), 2016-06-20 19:54:18]

On 2016/06/20 17:59:25, Scott Hess wrote:
> LGTM, with one concern.
> 
> My concern is whether there are both OS-version interactions and SDK-version
> interactions.  Like could SDK-version cause an older SQLite version to be used
> which may have latent bugs in mmap support?  I am not aware of any such bugs,
> but I don't really keep close track of SQLite changes outside the specific
> releases pulled into Chromium's tree, and anyhow Apple may have their own
> patches in there.
> 
> If running iOS version forces SQLite version, that addresses my concerns.  My
> assumption is that that's how things work.

There is a 1:1 mapping between iOS version and sqlite version.  (Each version of
iOS ships with a specific version of sqlite, and compiling the app with a
different SDK shouldn't affect that.)

If a new version of iOS has mmap-specific bugs, we'll probably need to
selectively disable support for that specific version.  Or we always have the
ability to fall back to compiling our own sqlite if we really want to.

[Scott Hess - ex-Googler, 2016-06-20 19:56:15]

On 2016/06/20 19:54:18, rohitrao wrote:
> On 2016/06/20 17:59:25, Scott Hess wrote:
> > LGTM, with one concern.
> > 
> > My concern is whether there are both OS-version interactions and SDK-version
> > interactions.  Like could SDK-version cause an older SQLite version to be
used
> > which may have latent bugs in mmap support?  I am not aware of any such
bugs,
> > but I don't really keep close track of SQLite changes outside the specific
> > releases pulled into Chromium's tree, and anyhow Apple may have their own
> > patches in there.
> > 
> > If running iOS version forces SQLite version, that addresses my concerns. 
My
> > assumption is that that's how things work.
> 
> There is a 1:1 mapping between iOS version and sqlite version.  (Each version
of
> iOS ships with a specific version of sqlite, and compiling the app with a
> different SDK shouldn't affect that.)
> 
> If a new version of iOS has mmap-specific bugs, we'll probably need to
> selectively disable support for that specific version.  Or we always have the
> ability to fall back to compiling our own sqlite if we really want to.

OK, then LGTM.

[rohitrao (ping after 24h), 2016-06-21 07:20:13]

The CQ bit was checked by rohitrao@chromium.org

[commit-bot: I haz the power, 2016-06-21 07:20:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2083543003/1

[commit-bot: I haz the power, 2016-06-21 07:26:13]

Description was changed from

==========
Updates SQL code now that mmap is supported on iOS.

BUG=621065
TEST=None
==========

to

==========
Updates SQL code now that mmap is supported on iOS.

BUG=621065
TEST=None
==========

[commit-bot: I haz the power, 2016-06-21 07:26:14]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-21 07:27:49]

Description was changed from

==========
Updates SQL code now that mmap is supported on iOS.

BUG=621065
TEST=None
==========

to

==========
Updates SQL code now that mmap is supported on iOS.

BUG=621065
TEST=None

Committed: https://crrev.com/83d6b83a933f827466509945ad1ca68f0053fd93
Cr-Commit-Position: refs/heads/master@{#400915}
==========

[commit-bot: I haz the power, 2016-06-21 07:27:50]

Patchset 1 (id:??) landed as
https://crrev.com/83d6b83a933f827466509945ad1ca68f0053fd93
Cr-Commit-Position: refs/heads/master@{#400915}