Use MB on all of the blink bots.

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

 [
   {
     "cmd": [
       "python",
       "-u",
       "[BUILD]\\scripts\\slave\\kill_processes.py"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "taskkill"
   },
@@ skipping 104 matching lines @@
   },
   {
     "cmd": [
       "python",
       "-u",
       "[DEPOT_TOOLS]\\gclient.py",
       "runhooks"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
+      "GYP_CHROMIUM_NO_ACTION": "1",
       "GYP_DEFINES": "chromium_win_pch=0 component=shared_library fastbuild=1 gomadir='[BUILD]\\goma' target_arch=ia32 test_isolation_mode=prepare use_goma=1"
     },
     "name": "gclient runhooks"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport shutil\nimport sys\nshutil.copy(sys.argv[1], sys.argv[2])\n",
       "[SLAVE_BUILD]\\src\\testing\\buildbot\\chromium.webkit.json",
@@ skipping 58 matching lines @@
       "[SLAVE_BUILD]\\src\\out\\Debug",
       "--clean-isolated-files"
     ],
     "cwd": "[SLAVE_BUILD]",
     "name": "clean isolated files"
   },
   {
     "cmd": [
       "python",
       "-u",
+      "[SLAVE_BUILD]\\src\\tools\\mb\\mb.py",
+      "gen",
+      "-m",
+      "chromium.webkit",
+      "-b",
+      "WebKit Win 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"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
       "[BUILD]\\scripts\\slave\\compile.py",
       "--target",
       "Debug",
       "--src-dir",
       "[SLAVE_BUILD]\\src",
       "--build-tool",
       "ninja",
       "--compiler",
       "goma",
       "--goma-jsonstatus",
@@ skipping 97 matching lines @@
     "~followup_annotations": [
       "@@@STEP_TEXT@WebKit Win7 (dbg)@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]