Reland of Switch CrWinClang to gn again.

Reland of Switch CrWinClang to gn again. (patchset #1 id:1 of https://codereview.chromium.org/2049583002/ )

Reason for revert:
goma bug might be fixed now.

Original issue's description:
> Revert of Switch CrWinClang to gn again. (patchset #1 id:1 of https://codereview.chromium.org/2043743003/ )
>
> Reason for revert:
> goma miscompiles things in optimized clang-cl builds if -imsvc is used (which the gn build uses but the gyp build doesn't), see https://crbug.com/618038
>
> Original issue's description:
> > Switch CrWinClang to gn again.
> >
> > This relands parts of https://codereview.chromium.org/1947183004/
> > Now that clobber runs as a separate step before runhooks, swarming should work
> > on gn clobber bots.
> >
> > BUG=498033
> >
> > Committed: https://crrev.com/9b6d81f1e5b090fbc9eabc88972d1e6cc4369c94
> > Cr-Commit-Position: refs/heads/master@{#398148}
>
> TBR=dpranke@chromium.org
> # Not skipping CQ checks because original CL landed more than 1 days ago.
> BUG=498033
>
> Committed: https://crrev.com/ab4b1d0c4343dae872c6406263f8aa9b7d550f3d
> Cr-Commit-Position: refs/heads/master@{#398456}

TBR=dpranke@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=498033
Committed: https://crrev.com/91519789ec3c51284a52167facb6c2dfc42b27ac
Cr-Commit-Position: refs/heads/master@{#400972}

[Nico, 2016-06-21 11:43:43]

The CQ bit was checked by thakis@chromium.org

[Nico, 2016-06-21 11:43:43]

Created Reland of Switch CrWinClang to gn again.

[commit-bot: I haz the power, 2016-06-21 11:43:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/2081973002/1

[commit-bot: I haz the power, 2016-06-21 13:00:20]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-06-21 13:02:30]

Description was changed from

==========
Reland of Switch CrWinClang to gn again. (patchset #1 id:1 of
https://codereview.chromium.org/2049583002/ )

Reason for revert:
goma bug might be fixed now.

Original issue's description:
> Revert of Switch CrWinClang to gn again. (patchset #1 id:1 of
https://codereview.chromium.org/2043743003/ )
> 
> Reason for revert:
> goma miscompiles things in optimized clang-cl builds if -imsvc is used (which
the gn build uses but the gyp build doesn't), see https://crbug.com/618038
> 
> Original issue's description:
> > Switch CrWinClang to gn again.
> >
> > This relands parts of https://codereview.chromium.org/1947183004/
> > Now that clobber runs as a separate step before runhooks, swarming should
work
> > on gn clobber bots.
> >
> > BUG=498033
> >
> > Committed: https://crrev.com/9b6d81f1e5b090fbc9eabc88972d1e6cc4369c94
> > Cr-Commit-Position: refs/heads/master@{#398148}
> 
> TBR=dpranke@chromium.org
> # Not skipping CQ checks because original CL landed more than 1 days ago.
> BUG=498033
> 
> Committed: https://crrev.com/ab4b1d0c4343dae872c6406263f8aa9b7d550f3d
> Cr-Commit-Position: refs/heads/master@{#398456}

TBR=dpranke@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=498033
==========

to

==========
Reland of Switch CrWinClang to gn again. (patchset #1 id:1 of
https://codereview.chromium.org/2049583002/ )

Reason for revert:
goma bug might be fixed now.

Original issue's description:
> Revert of Switch CrWinClang to gn again. (patchset #1 id:1 of
https://codereview.chromium.org/2043743003/ )
>
> Reason for revert:
> goma miscompiles things in optimized clang-cl builds if -imsvc is used (which
the gn build uses but the gyp build doesn't), see https://crbug.com/618038
>
> Original issue's description:
> > Switch CrWinClang to gn again.
> >
> > This relands parts of https://codereview.chromium.org/1947183004/
> > Now that clobber runs as a separate step before runhooks, swarming should
work
> > on gn clobber bots.
> >
> > BUG=498033
> >
> > Committed: https://crrev.com/9b6d81f1e5b090fbc9eabc88972d1e6cc4369c94
> > Cr-Commit-Position: refs/heads/master@{#398148}
>
> TBR=dpranke@chromium.org
> # Not skipping CQ checks because original CL landed more than 1 days ago.
> BUG=498033
>
> Committed: https://crrev.com/ab4b1d0c4343dae872c6406263f8aa9b7d550f3d
> Cr-Commit-Position: refs/heads/master@{#398456}

TBR=dpranke@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=498033

Committed: https://crrev.com/91519789ec3c51284a52167facb6c2dfc42b27ac
Cr-Commit-Position: refs/heads/master@{#400972}
==========

[commit-bot: I haz the power, 2016-06-21 13:02:31]

Patchset 1 (id:??) landed as
https://crrev.com/91519789ec3c51284a52167facb6c2dfc42b27ac
Cr-Commit-Position: refs/heads/master@{#400972}

[Dirk Pranke, 2016-06-21 16:18:19]

lgtm