WebRTC: Use goma from cipd

scripts/slave/recipes/webrtc/standalone.expected/client_webrtc_mac64_release__gn_.json

 [
   {
     "cmd": [
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/ios/host_info.py",
       "--json-file",
       "/path/to/tmp/json"
     ],
     "name": "host and tools info",
     "~followup_annotations": [
       "@@@STEP_TEXT@<br />OS X 1.2.3, Xcode 6.7.8 (5D342509a)@@@",
@@ skipping 108 matching lines @@
       "-u",
       "[DEPOT_TOOLS]/gn.py",
       "--root=[SLAVE_BUILD]/src",
       "gen",
       "//out/Release",
       "--args=ffmpeg_branding=\"Chrome\" rtc_use_h264=true is_debug=false target_cpu=\"x64\" use_goma=true goma_dir=\"[BUILD]/goma\""
     ],
     "name": "gn"
   },
   {
+    "cmd": [],
+    "name": "ensure_goma"
+  },
+  {
+    "cmd": [
+      "python",
+      "-u",
+      "RECIPE_MODULE[build::cipd]/resources/bootstrap.py",
+      "--platform",
+      "mac-amd64",
+      "--dest-directory",
+      "[SLAVE_BUILD]/cipd",
+      "--json-output",
+      "/path/to/tmp/json"
+    ],
+    "name": "ensure_goma.install cipd",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@1@@@",
+      "@@@STEP_TEXT@cipd instance_id: 40-chars-fake-of-the-package-instance_id@@@",
+      "@@@STEP_LOG_LINE@json.output@{@@@",
+      "@@@STEP_LOG_LINE@json.output@  \"executable\": \"[SLAVE_BUILD]/cipd/cipd\", @@@",
+      "@@@STEP_LOG_LINE@json.output@  \"instance_id\": \"40-chars-fake-of-the-package-instance_id\"@@@",
+      "@@@STEP_LOG_LINE@json.output@}@@@",
+      "@@@STEP_LOG_END@json.output@@@"
+    ]
+  },
+  {
+    "cmd": [
+      "[SLAVE_BUILD]/cipd/cipd",
+      "ensure",
+      "--root",
+      "[CACHE]/cipd/goma",
+      "--list",
+      "infra_internal/goma/client/mac-amd64 release",
+      "--json-output",
+      "/path/to/tmp/json",
+      "--service-account-json",
+      "/creds/service_accounts/service-account-goma-client.json"
+    ],
+    "name": "ensure_goma.ensure_installed",
+    "~followup_annotations": [
+      "@@@STEP_NEST_LEVEL@1@@@",
+      "@@@STEP_LOG_LINE@json.output@{@@@",
+      "@@@STEP_LOG_LINE@json.output@  \"result\": [@@@",
+      "@@@STEP_LOG_LINE@json.output@    {@@@",
+      "@@@STEP_LOG_LINE@json.output@      \"instance_id\": \"resolved-instance_id-of-release---------\", @@@",
+      "@@@STEP_LOG_LINE@json.output@      \"package\": \"infra_internal/goma/client/mac-amd64\"@@@",
+      "@@@STEP_LOG_LINE@json.output@    }@@@",
+      "@@@STEP_LOG_LINE@json.output@  ]@@@",
+      "@@@STEP_LOG_LINE@json.output@}@@@",
+      "@@@STEP_LOG_END@json.output@@@"
+    ]
+  },
+  {
     "allow_subannotations": true,
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[build]/scripts/slave/clang_revision.py",
       "--src-dir",
       "[SLAVE_BUILD]/src",
       "--output-json",
       "/path/to/tmp/json"
     ],
@@ skipping 28 matching lines @@
       "[GOMA_CACHE]",
       "--build-tool",
       "ninja",
       "--compiler",
       "goma-clang",
       "--goma-jsonstatus",
       "/path/to/tmp/json",
       "--goma-service-account-json-file",
       "/creds/service_accounts/service-account-goma-client.json",
       "--goma-dir",
-      "[BUILD]/goma",
+      "[CACHE]/cipd/goma",
       "--",
       "all"
     ],
     "env": {
       "GOMA_SERVICE_ACCOUNT_JSON_FILE": "/creds/service_accounts/service-account-goma-client.json"
     },
     "name": "compile",
     "~followup_annotations": [
       "@@@STEP_LOG_LINE@json.output (invalid)@null@@@",
       "@@@STEP_LOG_END@json.output (invalid)@@@"
     ]
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]