Stop to use contextmanager for goma.build_with_goma

scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_linux64_debug_forced.json

 [
   {
     "cmd": [
       "python",
       "-u",
       "\nimport sys, os\npath = sys.argv[1]\nmode = int(sys.argv[2])\nif not os.path.isdir(path):\n  if os.path.exists(path):\n    print \"%s exists but is not a dir\" % path\n    sys.exit(1)\n  os.makedirs(path, mode)\n",
       "[BUILDER_CACHE]/Linux64_Debug",
       "511"
     ],
     "name": "makedirs checkout path",
@@ skipping 227 matching lines @@
       "@@@STEP_LOG_LINE@swarming-targets-file.txt@test_support_unittests@@@",
       "@@@STEP_LOG_LINE@swarming-targets-file.txt@tools_unittests@@@",
       "@@@STEP_LOG_LINE@swarming-targets-file.txt@video_engine_tests@@@",
       "@@@STEP_LOG_LINE@swarming-targets-file.txt@voice_engine_unittests@@@",
       "@@@STEP_LOG_LINE@swarming-targets-file.txt@webrtc_nonparallel_tests@@@",
       "@@@STEP_LOG_LINE@swarming-targets-file.txt@xmllite_xmpp_unittests@@@",
       "@@@STEP_LOG_END@swarming-targets-file.txt@@@"
     ]
   },
   {
-    "cmd": [
-      "python",
-      "-u",
-      "\nimport multiprocessing\nimport sys\n\njob_limit = 200\nif sys.platform.startswith('linux'):\n  # Use 80 for linux not to load goma backend.\n  job_limit = 80\n\ntry:\n  jobs = min(job_limit, multiprocessing.cpu_count() * 10)\nexcept NotImplementedError:\n  jobs = 50\n\nprint jobs\n"
-    ],
-    "name": "calculate the number of recommended jobs",
-    "stdout": "/path/to/tmp/",
-    "~followup_annotations": [
-      "@@@STEP_LOG_LINE@python.inline@@@@",
-      "@@@STEP_LOG_LINE@python.inline@import multiprocessing@@@",
-      "@@@STEP_LOG_LINE@python.inline@import sys@@@",
-      "@@@STEP_LOG_LINE@python.inline@@@@",
-      "@@@STEP_LOG_LINE@python.inline@job_limit = 200@@@",
-      "@@@STEP_LOG_LINE@python.inline@if sys.platform.startswith('linux'):@@@",
-      "@@@STEP_LOG_LINE@python.inline@  # Use 80 for linux not to load goma backend.@@@",
-      "@@@STEP_LOG_LINE@python.inline@  job_limit = 80@@@",
-      "@@@STEP_LOG_LINE@python.inline@@@@",
-      "@@@STEP_LOG_LINE@python.inline@try:@@@",
-      "@@@STEP_LOG_LINE@python.inline@  jobs = min(job_limit, multiprocessing.cpu_count() * 10)@@@",
-      "@@@STEP_LOG_LINE@python.inline@except NotImplementedError:@@@",
-      "@@@STEP_LOG_LINE@python.inline@  jobs = 50@@@",
-      "@@@STEP_LOG_LINE@python.inline@@@@",
-      "@@@STEP_LOG_LINE@python.inline@print jobs@@@",
-      "@@@STEP_LOG_END@python.inline@@@"
-    ]
-  },
-  {
     "cmd": [],
     "name": "preprocess_for_goma"
   },
   {
     "cmd": [
       "python",
       "-u",
       "[CACHE]/cipd/goma/goma_ctl.py",
       "restart"
     ],
@@ skipping 22 matching lines @@
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "preprocess_for_goma.start cloudtail",
     "~followup_annotations": [
       "@@@STEP_NEST_LEVEL@1@@@"
     ]
   },
   {
     "cmd": [
+      "python",
+      "-u",
+      "\nimport multiprocessing\nimport sys\n\njob_limit = 200\nif sys.platform.startswith('linux'):\n  # Use 80 for linux not to load goma backend.\n  job_limit = 80\n\ntry:\n  jobs = min(job_limit, multiprocessing.cpu_count() * 10)\nexcept NotImplementedError:\n  jobs = 50\n\nprint jobs\n"
+    ],
+    "name": "calculate the number of recommended jobs",
+    "stdout": "/path/to/tmp/",
+    "~followup_annotations": [
+      "@@@STEP_LOG_LINE@python.inline@@@@",
+      "@@@STEP_LOG_LINE@python.inline@import multiprocessing@@@",
+      "@@@STEP_LOG_LINE@python.inline@import sys@@@",
+      "@@@STEP_LOG_LINE@python.inline@@@@",
+      "@@@STEP_LOG_LINE@python.inline@job_limit = 200@@@",
+      "@@@STEP_LOG_LINE@python.inline@if sys.platform.startswith('linux'):@@@",
+      "@@@STEP_LOG_LINE@python.inline@  # Use 80 for linux not to load goma backend.@@@",
+      "@@@STEP_LOG_LINE@python.inline@  job_limit = 80@@@",
+      "@@@STEP_LOG_LINE@python.inline@@@@",
+      "@@@STEP_LOG_LINE@python.inline@try:@@@",
+      "@@@STEP_LOG_LINE@python.inline@  jobs = min(job_limit, multiprocessing.cpu_count() * 10)@@@",
+      "@@@STEP_LOG_LINE@python.inline@except NotImplementedError:@@@",
+      "@@@STEP_LOG_LINE@python.inline@  jobs = 50@@@",
+      "@@@STEP_LOG_LINE@python.inline@@@@",
+      "@@@STEP_LOG_LINE@python.inline@print jobs@@@",
+      "@@@STEP_LOG_END@python.inline@@@"
+    ]
+  },
+  {
+    "cmd": [
       "RECIPE_PACKAGE_REPO[depot_tools]/ninja",
+      "-j",
+      "50",
       "-w",
       "dupbuild=err",
       "-C",
-      "[BUILDER_CACHE]/Linux64_Debug/src/out/Debug",
-      "-j",
-      "50"
+      "[BUILDER_CACHE]/Linux64_Debug/src/out/Debug"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "compile with ninja"
   },
   {
     "cmd": [],
     "name": "postprocess_for_goma"
   },
@@ skipping 49 matching lines @@
       "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/upload_goma_logs.py",
       "--upload-compiler-proxy-info",
       "--json-status",
       "[CACHE]/cipd/goma/jsonstatus",
       "--ninja-log-outdir",
       "[BUILDER_CACHE]/Linux64_Debug/src/out/Debug",
       "--ninja-log-compiler",
       "goma",
       "--ninja-log-command",
-      "['RECIPE_PACKAGE_REPO[depot_tools]/ninja', '-w', 'dupbuild=err', '-C', '[BUILDER_CACHE]/Linux64_Debug/src/out/Debug', '-j', 50]",
+      "['RECIPE_PACKAGE_REPO[depot_tools]/ninja', '-j', 50, '-w', 'dupbuild=err', '-C', '[BUILDER_CACHE]/Linux64_Debug/src/out/Debug']",
       "--ninja-log-exit-status",
       "0",
       "--buildbot-buildername",
       "Linux64 Debug",
       "--buildbot-mastername",
       "client.webrtc",
       "--buildbot-slavename",
       "slavename"
     ],
     "env": {
@@ skipping 2796 matching lines @@
       "@@@STEP_LOG_END@json.output@@@",
       "@@@STEP_LINK@shard #0 isolated out@blah@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]