Revert of Fix some build symbol configuration.

Revert of Fix some build symbol configuration. (patchset #3 id:40001 of https://codereview.chromium.org/1179393004/)

Reason for revert:
Broke the Linux GN Clobber bot:

http://build.chromium.org/p/chromium.linux/builders/Linux%20GN%20Clobber/builds/1271/steps/compile/logs/stdio

ninja: error: '../../build/linux/dump_app_syms', needed by 'obj/chrome/linux_symbols.inputdeps.stamp', missing and no known rule to make it

Original issue's description:
> Fix some build symbol configuration.
>
> Remove -gdwarf-4 from GYP build. This is the default for GCC 4.8 which is now required, so this command-line argument is redundant.
>
> Only set use_debug_fission in the GN build in debug mode. This matches GYP. Release mode symbols will be non-fission.
>
> Implement linux_symbols target in GN. Convert dump_app_syms from sh to Python for better GN usability, and it's more readable for normal programmers on the team.
>
> BUG=
>
> Committed: https://crrev.com/950889c01dd934acf28bce29ea6db75610a8c441
> Cr-Commit-Position: refs/heads/master@{#334510}

TBR=thakis@chromium.org,brettw@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=

Committed: https://crrev.com/520e8fd6084a0b3f1ec1011273730c4c6e392d09
Cr-Commit-Position: refs/heads/master@{#334522}

[Lei Zhang, 2015-06-16 01:09:47]

Created Revert of Fix some build symbol configuration.

[commit-bot: I haz the power, 2015-06-16 01:10:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1182783006/1

[commit-bot: I haz the power, 2015-06-16 01:12:04]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-16 01:12:47]

Patchset 1 (id:??) landed as
https://crrev.com/520e8fd6084a0b3f1ec1011273730c4c6e392d09
Cr-Commit-Position: refs/heads/master@{#334522}