Use MB on all of the blink bots.

scripts/slave/recipes/chromium.expected/full_chromium_webkit_WebKit_Mac_Builder__dbg_.json

Index: scripts/slave/recipes/chromium.expected/full_chromium_webkit_WebKit_Mac_Builder__dbg_.json
diff --git a/scripts/slave/recipes/chromium.expected/full_chromium_webkit_WebKit_Mac_Builder__dbg_.json b/scripts/slave/recipes/chromium.expected/full_chromium_webkit_WebKit_Mac_Builder__dbg_.json
index 8c03e6e29bbef3ff5d3db3caece33c67b01e6cfe..a9169cbbb0e61160c79e7fa965483bec6dc339d1 100644
--- a/scripts/slave/recipes/chromium.expected/full_chromium_webkit_WebKit_Mac_Builder__dbg_.json
+++ b/scripts/slave/recipes/chromium.expected/full_chromium_webkit_WebKit_Mac_Builder__dbg_.json
@@ -113,6 +113,7 @@
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
+      "GYP_CHROMIUM_NO_ACTION": "1",
       "GYP_DEFINES": "clang=1 component=shared_library gomadir='[BUILD]/goma' target_arch=x64 test_isolation_mode=prepare use_goma=1"
     },
     "name": "gclient runhooks"
@@ -188,6 +189,27 @@
     "name": "clean isolated files"
   },
   {
+    "cmd": [
+      "python",
+      "-u",
+      "[SLAVE_BUILD]/src/tools/mb/mb.py",
+      "gen",
+      "-m",
+      "chromium.webkit",
+      "-b",
+      "WebKit Mac Builder (dbg)",
+      "--config-file",
+      "[SLAVE_BUILD]/src/tools/mb/mb_config.pyl",
+      "--goma-dir",
+      "[BUILD]/goma",
+      "--swarming-targets-file",
+      "browser_tests\n",
+      "//out/Debug"
+    ],
+    "cwd": "[SLAVE_BUILD]",
+    "name": "generate_build_files"
+  },
+  {
     "allow_subannotations": true,
     "cmd": [
       "python",