Make asan=1 GYP flag enforce -gline-tables-only.

Make asan=1 GYP flag enforce -gline-tables-only.
Having at least this level of debug info is a must in order to have line numbers in the symbolized ASan reports.
On the other hand the binaries will be smaller than those built with -g, so we'll be able to copy the binaries between bots.
Users of asan_symbolize.py will need to set LLVM_SYMBOLIZER_PATH in order to have full function names with -gline-tables-only
(see http://dev.chromium.org/developers/testing/addresssanitizer)

BUG=128544
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=179326

[Alexander Potapenko, 2013-01-28 14:02:19]

Nico, PTAL

Abhishek, Denis, FYI.

[Nico, 2013-01-28 21:43:44]

lgtm

[glotov, 2013-01-29 09:03:36]

lgtm

lgtm