Adds ability to build for asan with gn

build/config/sanitizers/BUILD.gn

Index: build/config/sanitizers/BUILD.gn
diff --git a/build/config/sanitizers/BUILD.gn b/build/config/sanitizers/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..035bdf3558baab4209c331de754d8f7738e998fb
--- /dev/null
+++ b/build/config/sanitizers/BUILD.gn
@@ -0,0 +1,23 @@
+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+group("deps") {

[brettw, 2014/10/28 23:55:16]

Can you provide a comment here about how this is the stuff required to link into
executables and shared libraries when running under asan, and that it will
conditionally be empty in other cases so targets can unconditionally depend on
it.

[sky, 2014/10/29 00:02:30]

Done.

+  if (is_asan) {
+    public_configs = [ ":sanitizer_options_link_helper" ]
+    deps = [ ":options_sources" ]
+  }
+}
+
+config("sanitizer_options_link_helper") {
+  ldflags = [ "-Wl,-u_sanitizer_options_link_helper", "-fsanitize=address" ]
+}
+
+source_set("options_sources") {
+  visibility = [ ":deps" ]
+  sources = [ "//build/sanitizers/sanitizer_options.cc" ]
+
+  if (is_tsan) {
+    sources += [ "//build/sanitizers/tsan_suppressions.cc" ]
+  }
+}