V8: Switch blink downstream bots to use mb

scripts/slave/recipes/blink_downstream.expected/webkit_tests_unexpected_error.json

Index: scripts/slave/recipes/blink_downstream.expected/webkit_tests_unexpected_error.json
diff --git a/scripts/slave/recipes/blink_downstream.expected/webkit_tests_unexpected_error.json b/scripts/slave/recipes/blink_downstream.expected/webkit_tests_unexpected_error.json
index 6286cedb738bb3bdd4f65250485a0235a3fc5b2c..b7aba698df968673982e4b34d8ec3c97f7c7217b 100644
--- a/scripts/slave/recipes/blink_downstream.expected/webkit_tests_unexpected_error.json
+++ b/scripts/slave/recipes/blink_downstream.expected/webkit_tests_unexpected_error.json
@@ -117,6 +117,7 @@
     "cwd": "[SLAVE_BUILD]/src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json",
+      "GYP_CHROMIUM_NO_ACTION": "1",
       "GYP_DEFINES": "component=static_library gomadir='[BUILD]/goma' target_arch=x64 use_goma=1",
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
@@ -126,6 +127,27 @@
     "cmd": [
       "python",
       "-u",
+      "[SLAVE_BUILD]/src/tools/mb/mb.py",
+      "gen",
+      "-m",
+      "client.v8.fyi",
+      "-b",
+      "V8-Blink Linux 64",
+      "--config-file",
+      "[SLAVE_BUILD]/src/tools/mb/mb_config.pyl",
+      "--goma-dir",
+      "[BUILD]/goma",
+      "//out/Release"
+    ],
+    "env": {
+      "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
+    },
+    "name": "generate_build_files (with patch)"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/tools/runit.py",
       "--show-path",
       "python",
@@ -156,7 +178,7 @@
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
-    "name": "compile",
+    "name": "compile (with patch)",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output (invalid)@null@@@",
       "@@@STEP_LOG_END@json.output (invalid)@@@"