Add both node paths to both Polymer steps.

scripts/slave/recipes/polymer.expected/polymer-win.json

 [
   {
    "cmd": ["python", "-u", "[DEPOT_TOOLS_ROOT]\\gclient.py", "config", "--spec", "cache_dir = None\ndeps_os = {}\nhooks = []\nsolutions = [{'custom_deps': {}, 'custom_vars': {}, 'deps_file': '', 'managed': True, 'name': 'CustomElements', 'safesync_url': None, 'url': 'https://github.com/Polymer/CustomElements.git'}, {'custom_deps': {}, 'custom_vars': {}, 'deps_file': '', 'managed': True, 'name': 'HTMLImports', 'safesync_url': None, 'url': 'https://github.com/Polymer/HTMLImports.git'}, {'custom_deps': {}, 'custom_vars': {}, 'deps_file': '', 'managed': True, 'name': 'PointerEvents', 'safesync_url': None, 'url': 'https://github.com/Polymer/PointerEvents.git'}, {'custom_deps': {}, 'custom_vars': {}, 'deps_file': '', 'managed': True, 'name': 'PointerGestures', 'safesync_url': None, 'url': 'https://github.com/Polymer/PointerGestures.git'}, {'custom_deps': {}, 'custom_vars': {}, 'deps_file': '', 'managed': True, 'name': 'ShadowDOM', 'safesync_url': None, 'url': 'https://github.com/Polymer/ShadowDOM.git'}, {'custom_deps': {}, 'custom_vars': {}, 'deps_file': '', 'managed': True, 'name': 'mdv', 'safesync_url': None, 'url': 'https://github.com/Polymer/mdv.git'}, {'custom_deps': {}, 'custom_vars': {}, 'deps_file': '', 'managed': True, 'name': 'platform', 'safesync_url': None, 'url': 'https://github.com/Polymer/platform.git'}, {'custom_deps': {}, 'custom_vars': {}, 'deps_file': '', 'managed': True, 'name': 'polymer', 'safesync_url': None, 'url': 'https://github.com/Polymer/polymer.git'}]\ntarget_os = []\ntarget_os_only = False"],
    "name": "gclient setup",
    "seed_steps": ["gclient setup", "gclient revert", "gclient sync", "submodule update"]
   },
   {
    "cmd": ["python", "-u", "[BUILD_ROOT]\\scripts\\slave\\gclient_safe_revert.py", ".", "[DEPOT_TOOLS_ROOT]\\gclient.bat"],
    "name": "gclient revert"
   },
   {
    "cmd": ["python", "-u", "[DEPOT_TOOLS_ROOT]\\gclient.py", "sync", "--nohooks"],
    "name": "gclient sync"
   },
   {
    "cmd": ["python", "-u", "[DEPOT_TOOLS_ROOT]\\gclient.py", "recurse", "git", "submodule", "update", "--init", "--recursive"],
    "name": "submodule update"
   },
   {
    "cmd": ["npm.cmd", "install"],
    "cwd": "[SLAVE_BUILD_ROOT]\\polymer",
-   "env": {"PATH": "C:\\Program Files (x86)\\nodejs;%(PATH)s"},
+   "env": {"PATH": "C:\\Program Files (x86)\\nodejs;C:\\Users\\chrome-bot\\AppData\\Roaming\\npm;%(PATH)s"},
    "name": "update-install"
   },
   {
    "allow_subannotations": true,
    "cmd": ["grunt.cmd", "test-buildbot"],
    "cwd": "[SLAVE_BUILD_ROOT]\\polymer",
-   "env": {"PATH": "C:\\Users\\chrome-bot\\AppData\\Roaming\\npm;%(PATH)s"},
+   "env": {"PATH": "C:\\Program Files (x86)\\nodejs;C:\\Users\\chrome-bot\\AppData\\Roaming\\npm;%(PATH)s"},
    "name": "test"
   }
 ]