Merge v8_optimized_debug 1 and 2

Merge v8_optimized_debug 1 and 2

All builders that used level 1 should meanwhile define
v8_enable_slow_dchecks, and so they can use level 2 without losing
coverage. Level 2, however, is considerably faster, so we want to use it
on those builders as well. The make optdebug setting is not affected by
this change.

BUG=none
R=machenbach@chromium.org
LOG=n

Committed: https://crrev.com/aeb09e6dcfbdbad68e1766a4433c992f94b129c5
Cr-Commit-Position: refs/heads/master@{#26019}

[Michael Achenbach, 2015-01-12 08:55:42]

LGTM with nits:

https://codereview.chromium.org/847753002/diff/1/Makefile
File Makefile (right):

https://codereview.chromium.org/847753002/diff/1/Makefile#newcode112
Makefile:112: ifeq ($(optdebug), on)
Wonder if this is necessary. We have two modes already, debug and optdebug in
the top-level Makefile that cover the two levels. I don't see a reason why one
would need this switch now. Delete?

https://codereview.chromium.org/847753002/diff/1/Makefile#newcode433
Makefile:433: $(if $(findstring optdebug,$@),-Dv8_optimized_debug=1,) \
nit: Can you maybe get rid of the tabs?

[jochen (gone - plz use gerrit), 2015-01-12 08:58:23]

the entire Makefile uses tabs - I don't think retabbing a single line is a good
idea

[jochen (gone - plz use gerrit), 2015-01-12 08:59:08]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-01-12 08:59:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/847753002/40001

[jochen (gone - plz use gerrit), 2015-01-12 09:06:28]

The CQ bit was unchecked by jochen@chromium.org

[jochen (gone - plz use gerrit), 2015-01-12 09:07:10]

meh, when inlining slow dchecks, the compiler figures out that some of them can
never be true

i guess that's a good thing, but it makes my patch fail to compile... fixing

[jochen (gone - plz use gerrit), 2015-01-12 09:30:24]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-01-12 09:31:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/847753002/60001

[Michael Achenbach, 2015-01-12 09:55:28]

lgtm

[commit-bot: I haz the power, 2015-01-12 09:58:39]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-01-12 09:58:50]

Patchset 4 (id:??) landed as
https://crrev.com/aeb09e6dcfbdbad68e1766a4433c992f94b129c5
Cr-Commit-Position: refs/heads/master@{#26019}