GN: BUILD.gn for system_wrappers

Also cleaned up some unneeded stuff from webrtc/base/BUILD.gn

BUG=3441
TEST=
Successful compilation of WebRTC as standalone:
gn gen out/Default --args="build_with_chromium=false" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false is_clang=true clang_use_chrome_plugins=false" && ninja -C out/Default

I built successfully from a Chromium checkout (with
https://codereview.chromium.org/321313006/ applied) using:
gn gen out/Default && ninja -C out/Default webrtc

R=brettw@chromium.org
TBR=niklas.enbom@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/20739004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6515 4adac7df-926f-26a2-2b94-8c16560cd09d
Roll chromium_revision 272489:277350 + fix sanitizer options

Rolling to this new Chromium revision required us to introduce
a sanitizer_options similar to the one in Chromium's base
(see https://code.google.com/p/chromium/codesearch#chromium/src/base/base.gyp&l=977
and https://codereview.chromium.org/238123003) in order
to get the same defaults for ASan and LSan. Without it
compilation will break since LeakSanitizer (LSan) is enabled by
default in Clang r209387 that is pulled with this roll.

I setup so that we pull in the sanitizer_options.cc and
tsan_suppressions.cc files using DEPS, so we don't have to maintain
them separately for now. We can still use our own TSan suppressions.txt
file as we do today with no changes needed.

This roll also brings in http://crrev.com/276676 so we can enable
GN build for WebRTC.

Overview of changes in Chrome DEPS:
$ svn diff http://src.chromium.org/chrome/trunk/src/DEPS -r 272489:277350

which can be compared with the output of:
$ svn cat http://webrtc.googlecode.com/svn/trunk/DEPS | grep chromium_deps | sed 's/^ *//' | sort | uniq

in a WebRTC checkout, gives the following relevant changes:
* third_party/android_tools 6fc0e1:c6e658
* third_party/libjpeg_turbo 263594:272637
* third_party/libyuv 1000:1007
* third_party/nss 271760:277057
* tools/gyp 1921:1927
* tools/swarming_client ae8085:aea506

The following also shows that Clang is upgraded from r206824 to r209387:
$ svn diff http://src.chromium.org/chrome/trunk/src/tools/clang/scripts/update.sh -r 272489:277350

BUG=3441
TEST=Trybots are not passing since after the recipe switch, SVN-based try jobs doesn't seem to support auto-detecting that a sync is needed if there's a DEPS change.
R=andrew@webrtc.org, pbos@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/12729004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6516 4adac7df-926f-26a2-2b94-8c16560cd09d
Add third_party/colorama to DEPS

In the chromium_revision DEPS roll CL
https://review.webrtc.org/12729004/ (r6516) the addition
of the third_party/colorama was missed since our trybots
currently cannot handle DEPS changes in tryjob patches
properly.
Adding third_party/colorama/src fixes the Android build.

TEST=Passing local compile with GYP_DEFINES="OS=android component=static_library fastbuild=1 target_arch=arm"
TBR=andrew@webrtc.org
BUG=

Review URL: https://webrtc-codereview.appspot.com/12819004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6517 4adac7df-926f-26a2-2b94-8c16560cd09d