Skia bots: use deps_os = 'all'

scripts/slave/recipes/skia/skia.expected/Build-Mac10.9-Clang-Arm7-Debug-iOS.json

 [
   {
     "cmd": [
       "git",
       "remote",
       "set-url",
       "origin",
       "https://skia.googlesource.com/skia.git"
     ],
     "cwd": "[SLAVE_BUILD]/skia",
@@ skipping 27 matching lines @@
     "cwd": "[SLAVE_BUILD]/skia",
     "name": "git clean"
   },
   {
     "cmd": [
       "python",
       "-u",
       "RECIPE_PACKAGE_REPO[depot_tools]/gclient.py",
       "config",
       "--spec",
-      "cache_dir = '[GIT_CACHE]'\nsolutions = [{'deps_file': 'DEPS', 'managed': False, 'name': 'skia', 'url': 'https://skia.googlesource.com/skia.git'}]"
+      "cache_dir = '[GIT_CACHE]'\ndeps_os = {'skia': 'all'}\nsolutions = [{'deps_file': 'DEPS', 'managed': False, 'name': 'skia', 'url': 'https://skia.googlesource.com/skia.git'}]"
     ],
     "cwd": "[SLAVE_BUILD]",
     "env": {
       "PATH": "%(PATH)s:RECIPE_PACKAGE_REPO[depot_tools]"
     },
     "name": "gclient setup"
   },
   {
     "cmd": [
       "python",
@@ skipping 83 matching lines @@
       "SKIA_OUT": "[SLAVE_BUILD]/skia/out/Build-Mac10.9-Clang-Arm7-Debug-iOS"
     },
     "name": "build iOSShell"
   },
   {
     "name": "$result",
     "recipe_result": null,
     "status_code": 0
   }
 ]