Hook up the tsan flag for the GN build.

build/gyp_chromium

Index: build/gyp_chromium
diff --git a/build/gyp_chromium b/build/gyp_chromium
index e62e0b7ad4dcdb93193e22043341e88f7cba8a27..c67a985817d93a9bf6f5c04351a0ac868b03197f 100755
--- a/build/gyp_chromium
+++ b/build/gyp_chromium
@@ -177,6 +177,7 @@ def GetArgsStringForGN(supplemental_files):
       ('buildtype', 'Official', 'is_official_build=true'),
       ('component', 'shared_library', 'is_component_build=true'),
       ('clang', '1', 'is_clang=true'),
+      ('disable_glibcxx_debug', '1', 'disable_glibcxx_debug=true'),
       ('target_arch', 'ia32', 'cpu_arch="x86"'),
       ('target_arch', 'x64', 'cpu_arch="x64" force_win64=true'),
       ('target_arch', 'arm', 'cpu_arch="arm"'),
@@ -191,6 +192,7 @@ def GetArgsStringForGN(supplemental_files):
       ('use_goma', '1', 'use_goma=true'),
       ('asan', '1', 'is_asan=true'),
       ('lsan', '1', 'is_lsan=true'),
+      ('tsan', '1', 'is_tsan=true'),
   ]
   for i in remap_cases:
     if i[0] in vars_dict and vars_dict[i[0]] == i[1]: