Add new site isolation trybot.

masters/master.tryserver.chromium.linux/master.cfg

Index: masters/master.tryserver.chromium.linux/master.cfg
diff --git a/masters/master.tryserver.chromium.linux/master.cfg b/masters/master.tryserver.chromium.linux/master.cfg
index dfc3d2c7a416d92cf61c20b06b08770fba9b5ba9..3fc015a0b235f44aa36643bba16f4555a3dc5b22 100644
--- a/masters/master.tryserver.chromium.linux/master.cfg
+++ b/masters/master.tryserver.chromium.linux/master.cfg
@@ -297,6 +297,13 @@ b_linux_chromium_asan_rel = {
   'slavebuilddir': 'linux_asan',
 }
 
+b_linux_site_isolation = {
+  'name': 'linux_site_isolation',
+  'factory': m_annotator.BaseFactory('chromium_trybot'),
+  # Share build directory with compatible existing builders to save space.
+  'slavebuilddir': 'linux',
+}
+
 b_linux_chromium_asan_rel_ng = {
   'name': 'linux_chromium_asan_rel_ng',
   'factory': m_annotator.BaseFactory('chromium_trybot'),
@@ -425,6 +432,7 @@ c['builders'] = [
   b_linux_full_bisect_builder,
   b_linux_nacl_sdk, b_linux_nacl_sdk_bionic,
   b_linux_nacl_sdk_build, b_linux_nacl_sdk_bionic_build,
+  b_linux_site_isolation,
   b_chromium_presubmit,
   b_tools_build_presubmit,
   b_infra_tester,