Compile v8 like "release" by default in debug builds.

Compile v8 like "release" by default in debug builds.

This change switches how we compile v8 by default in Debug builds
so that the compiler optimizations are enabled and much of the
still enabled to do some level of dcheck-like assertion checking).

This gives us a 5x speedup over the debug v8 for running the layout
tests, making debug times only 2x slower than release.

R=jamesr@chromium.org, jochen@chromium.org
BUG=254188
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=216287

[jochen (gone - plz use gerrit), 2013-07-30 20:12:16]

lgtm

[jamesr, 2013-07-30 20:23:04]

lgtm2

[commit-bot: I haz the power, 2013-07-30 21:06:48]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dpranke@chromium.org/21004010/1

[commit-bot: I haz the power, 2013-07-30 22:34:25]

Step "update" is always a major failure.
Look at the try server FAQ for more details.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win&number...

[commit-bot: I haz the power, 2013-07-31 01:09:27]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dpranke@chromium.org/21004010/23001

[commit-bot: I haz the power, 2013-07-31 01:58:55]

Step "update" is always a major failure.
Look at the try server FAQ for more details.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2013-07-31 03:19:04]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/dpranke@chromium.org/21004010/36001

[commit-bot: I haz the power, 2013-07-31 04:02:29]

Sorry for I got bad news for ya.
Compile failed with a clobber build on android_clang_dbg.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=android_cl...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[Dirk Pranke, 2013-08-07 22:09:10]

Committed patchset #3 manually as r216287 (presubmit successful).