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
Review URL: https://codereview.chromium.org/12087023

git-svn-id: http://src.chromium.org/svn/trunk/src/build@179326 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -2788,6 +2788,7 @@
                   '-fsanitize=address',
                   '-fno-omit-frame-pointer',
                   '-w',  # http://crbug.com/162783
+                  '-gline-tables-only',
                 ],
                 'ldflags': [
                   '-fsanitize=address',