Revert of Change PGO recipe to use MB now that it supports multiple phases.

scripts/slave/recipes/chromium_pgo.expected/full_tryserver_chromium_win_win_pgo.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\slave\\kill_processes.py"
     ],
     "name": "taskkill"
   },
   {
@@ skipping 139 matching lines @@
       "GYP_DEFINES": "buildtype=Official chrome_pgo_phase=1 component=static_library fastbuild=0 target_arch=ia32 use_goma=0",
       "GYP_MSVS_VERSION": "2015",
       "PATH": "[SLAVE_BUILD]\\src\\out\\Release;%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "gclient Runhooks: Instrumentation phase."
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[SLAVE_BUILD]\\src\\tools\\mb\\mb.py",
-      "gen",
-      "-m",
-      "tryserver.chromium.win",
-      "-b",
-      "win_pgo",
-      "--config-file",
-      "[SLAVE_BUILD]\\src\\tools\\mb\\mb_config.pyl",
-      "--phase",
-      "1",
-      "//out/Release"
+      "[SLAVE_BUILD]\\src\\build\\gyp_chromium.py"
     ],
-    "cwd": "[SLAVE_BUILD]\\src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "C:\\creds\\service_accounts\\service-account-goma-client.json",
-      "GYP_MSVS_VERSION": "2015"
+      "GYP_DEFINES": "buildtype=Official chrome_pgo_phase=1 component=static_library fastbuild=0 target_arch=ia32 use_goma=0",
+      "GYP_MSVS_VERSION": "2015",
+      "PATH": "[SLAVE_BUILD]\\src\\out\\Release;%(PATH)s"
     },
-    "name": "generate_build_files"
+    "name": "gyp_chromium"
   },
   {
     "cmd": [
       "python",
       "-u",
       "\nimport sys\nfrom common import chromium_utils # Error? See https://crbug.com/584783.\n\nchromium_utils.RemoveFilesWildcards(sys.argv[1], root=sys.argv[2])\n",
       "*.pg[cd]",
       "[SLAVE_BUILD]\\src\\out\\Release"
     ],
     "name": "rmwildcard *.pg[cd] in [SLAVE_BUILD]\\src\\out\\Release",
@@ skipping 480 matching lines @@
       "GYP_DEFINES": "buildtype=Official chrome_pgo_phase=2 component=static_library fastbuild=0 target_arch=ia32 use_goma=0",
       "GYP_MSVS_VERSION": "2015",
       "PATH": "%(PATH)s;RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "gclient Runhooks: Optimization phase."
   },
   {
     "cmd": [
       "python",
       "-u",
-      "[SLAVE_BUILD]\\src\\tools\\mb\\mb.py",
-      "gen",
-      "-m",
-      "tryserver.chromium.win",
-      "-b",
-      "win_pgo",
-      "--config-file",
-      "[SLAVE_BUILD]\\src\\tools\\mb\\mb_config.pyl",
-      "--phase",
-      "2",
-      "//out/Release"
+      "[SLAVE_BUILD]\\src\\build\\gyp_chromium.py"
     ],
-    "cwd": "[SLAVE_BUILD]\\src",
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "C:\\creds\\service_accounts\\service-account-goma-client.json",
+      "GYP_DEFINES": "buildtype=Official chrome_pgo_phase=2 component=static_library fastbuild=0 target_arch=ia32 use_goma=0",
       "GYP_MSVS_VERSION": "2015"
     },
-    "name": "generate_build_files (2)"
+    "name": "gyp_chromium (2)"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\tools\\runit.py",
       "--show-path",
       "python",
       "RECIPE_PACKAGE_REPO[build]\\scripts\\slave\\compile.py",
       "--gsutil-py-path",
@@ skipping 41 matching lines @@
       "{\"blamelist\": [\"cool_dev1337@chromium.org\", \"hax@chromium.org\"], \"branch\": \"\", \"buildername\": \"win_pgo\", \"buildnumber\": 571, \"issue\": 12853011, \"mastername\": \"tryserver.chromium.win\", \"patch_project\": \"chromium\", \"patchset\": 1, \"project\": \"chrome\", \"recipe\": \"chromium_pgo\", \"repository\": \"\", \"requester\": \"commit-bot@chromium.org\", \"revision\": \"HEAD\", \"rietveld\": \"https://codereview.chromium.org\", \"slavename\": \"TestSlavename\", \"workdir\": \"/path/to/workdir/TestSlavename\"}"
     ],
     "name": "package build"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]