diff --git a/tools/js/BUCK b/tools/js/BUCK
index ba4f19c..9eb0c91 100644
--- a/tools/js/BUCK
+++ b/tools/js/BUCK
@@ -1,14 +1,26 @@
 python_binary(
   name = 'bower2buck',
   main = 'bower2buck.py',
-  deps = ['//tools:util'],
+  deps = [
+    '//tools:util',
+    ":bowerutil",
+    ],
   visibility = ['PUBLIC'],
 )
 
+python_library(
+  name = 'bowerutil',
+  srcs = [ 'bowerutil.py' ],
+  visibility = [ 'PUBLIC' ],
+)
+
 python_binary(
   name = 'download_bower',
   main = 'download_bower.py',
-  deps = ['//tools:util'],
+  deps = [
+    '//tools:util',
+    ":bowerutil",
+  ],
   visibility = ['PUBLIC'],
 )
 
diff --git a/tools/js/BUILD b/tools/js/BUILD
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/tools/js/BUILD
diff --git a/tools/js/bower2bazel.py b/tools/js/bower2bazel.py
new file mode 100755
index 0000000..8682012
--- /dev/null
+++ b/tools/js/bower2bazel.py
@@ -0,0 +1,228 @@
+#!/usr/bin/env python
+# Copyright (C) 2015 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Suggested call sequence:
+
+python tools/js/bower2bazel.py -w lib/js/bower_archives.bzl -b lib/js/bower_components.bzl
+"""
+
+from __future__ import print_function
+
+import atexit
+import collections
+import json
+import hashlib
+import optparse
+import os
+import shutil
+import subprocess
+import sys
+import tempfile
+import glob
+import bowerutil
+
+# Map license names to our canonical names.
+license_map = {
+  "http://polymer.github.io/LICENSE.txt": "polymer",
+  "Apache-2.0": "Apache2.0",
+
+  # TODO(hanwen): remove these, and add appropriate license files under //lib
+  "BSD": "polymer",
+  "MIT": "polymer",
+}
+
+# list of licenses for packages that don't specify one in their bower.json file.
+package_licenses = {
+  "es6-promise": "es6-promise",
+  "fetch": "fetch",
+  "moment": "moment",
+  "page": "page.js",
+  "promise-polyfill": "promise-polyfill",
+  "webcomponentsjs": "polymer",   # self-identifies as BSD.
+}
+
+
+def build_bower_json(version_targets):
+  """Generate bower JSON file, return its path."""
+  bower_json = collections.OrderedDict()
+  bower_json['name'] = 'bower2buck-output'
+  bower_json['version'] = '0.0.0'
+  bower_json['description'] = 'Auto-generated bower.json for dependency management'
+  bower_json['private'] = True
+  bower_json['dependencies'] = {}
+
+  for v in version_targets:
+    fn = os.path.join("bazel-out/local-fastbuild/bin", v.lstrip("/").replace(":", "/"))
+    with open(fn) as f:
+      j = json.load(f)
+      if "" in j:
+        # drop dummy entries.
+        del j[""]
+      bower_json['dependencies'].update(j)
+
+  tmpdir = tempfile.mkdtemp()
+  ret = os.path.join(tmpdir, 'bower.json')
+  with open(ret, 'w') as f:
+    json.dump(bower_json, f, indent=2)
+  return ret
+
+
+def bower_command(args):
+  base = subprocess.check_output(["bazel", "info", "output_base"]).strip()
+  exp = os.path.join(base, "external", "bower", "*npm_binary.tgz")
+  fs = sorted(glob.glob(exp))
+  assert len(fs) == 1, "bower tarball not found or have multiple versions %s" % fs
+  return ["python", os.getcwd() + "/tools/js/run_npm_binary.py", sorted(fs)[0]] + args
+
+
+def main(args):
+  opts = optparse.OptionParser()
+  opts.add_option('-w', help='.bzl output for WORKSPACE')
+  opts.add_option('-b', help='.bzl output for //lib:BUILD')
+  opts, args = opts.parse_args()
+
+  target_str = subprocess.check_output([
+    "bazel", "query", "kind(bower_component_bundle, //polygerrit-ui/...)"])
+  seed_str = subprocess.check_output([
+    "bazel", "query", "attr(seed, 1, kind(bower_component, deps(//polygerrit-ui/...)))"])
+  targets = [s for s in target_str.split('\n') if s]
+  seeds = [s for s in seed_str.split('\n') if s]
+  prefix = "//lib/js:"
+  non_seeds = [s for s in seeds if not s.startswith(prefix)]
+  assert not non_seeds, non_seeds
+  seeds = set([s[len(prefix):] for s in seeds])
+
+  version_targets = [t + "-versions.json" for t in targets]
+
+  subprocess.check_call(['bazel', 'build'] + version_targets)
+  bower_json_path = build_bower_json(version_targets)
+  dir = os.path.dirname(bower_json_path)
+  cmd = bower_command(["install"])
+
+  build_out = sys.stdout
+  if opts.b:
+    build_out = open(opts.b + ".tmp", 'w')
+
+  ws_out = sys.stdout
+  if opts.b:
+    ws_out = open(opts.w + ".tmp", 'w')
+
+  header = """# DO NOT EDIT
+# generated with the following command:
+#
+#   %s
+#
+
+""" % ' '.join(sys.argv)
+
+  ws_out.write(header)
+  build_out.write(header)
+
+  oldwd = os.getcwd()
+  os.chdir(dir)
+  subprocess.check_call(cmd)
+
+  interpret_bower_json(seeds, ws_out, build_out)
+  ws_out.close()
+  build_out.close()
+
+  os.chdir(oldwd)
+  os.rename(opts.w + ".tmp", opts.w)
+  os.rename(opts.b + ".tmp", opts.b)
+
+
+def dump_workspace(data, seeds, out):
+  out.write('load("//tools/bzl:js.bzl", "bower_archive")\n')
+  out.write('def load_bower_archives():\n')
+
+  for d in data:
+    if d["name"] in seeds:
+      continue
+    out.write("""  bower_archive(
+    name = "%(name)s",
+    package = "%(normalized-name)s",
+    version = "%(version)s",
+    sha1 = "%(bazel-sha1)s")
+""" % d)
+
+
+def dump_build(data, seeds, out):
+  out.write('load("//tools/bzl:js.bzl", "bower_component")\n')
+  out.write('def define_bower_components():\n')
+  for d in data:
+    out.write("  bower_component(\n")
+    out.write("    name = \"%s\",\n" % d["name"])
+    out.write("    license = \"//lib:LICENSE-%s\",\n" % d["bazel-license"])
+    deps = sorted(d.get("dependencies", {}).keys())
+    if deps:
+      if len(deps) == 1:
+        out.write("    deps = [ \":%s\" ],\n" % deps[0])
+      else:
+        out.write("    deps = [\n")
+        for dep in deps:
+          out.write("      \":%s\",\n" % dep)
+        out.write("    ],\n")
+    if d["name"] in seeds:
+      out.write("    seed = True,\n")
+    out.write("  )\n")
+  # done
+
+
+def interpret_bower_json(seeds, ws_out, build_out):
+  out = subprocess.check_output(["find", "bower_components/", "-name", ".bower.json"])
+
+  data = []
+  for f in sorted(out.split('\n')):
+    if not f:
+      continue
+    pkg = json.load(open(f))
+    pkg_name = pkg["name"]
+
+    pkg["bazel-sha1"] = bowerutil.hash_bower_component(
+      hashlib.sha1(), os.path.dirname(f)).hexdigest()
+    license = pkg.get("license", None)
+    if type(license) == type([]):
+      # WTF? Some package specify a list of licenses. ("GPL", "MIT")
+      pick = license[0]
+      sys.stderr.write("package %s has multiple licenses: %s, picking %s" % (pkg_name, ", ".join(license), pick))
+      license = pick
+
+    if license:
+      license = license_map.get(license, license)
+    else:
+      if pkg_name not in package_licenses:
+        msg = "package %s does not specify license." % pkg_name
+        sys.stderr.write(msg)
+        raise Exception(msg)
+      license = package_licenses[pkg_name]
+
+    pkg["bazel-license"] = license
+
+    # TODO(hanwen): bower packages can also have 'fully qualified'
+    # names, ("PolymerElements/iron-ajax") as well as short names
+    # ("iron-ajax").  It is possible for bower.json files to refer to
+    # long names as their dependencies. If any package does this, we
+    # will have to either 1) strip off the prefix (typically github
+    # user?), or 2) build a map of short name <=> fully qualified
+    # name. For now, we just ignore the problem.
+    pkg["normalized-name"] = pkg["name"]
+    data.append(pkg)
+
+  dump_workspace(data, seeds, ws_out)
+  dump_build(data, seeds, build_out)
+
+
+if __name__ == '__main__':
+  main(sys.argv[1:])
diff --git a/tools/js/bower2buck.py b/tools/js/bower2buck.py
index 81072da..57da475 100755
--- a/tools/js/bower2buck.py
+++ b/tools/js/bower2buck.py
@@ -78,7 +78,7 @@
     self.version = bower_json['version']
     self.deps = bower_json.get('dependencies', {})
     self.license = bower_json.get('license', 'NO LICENSE')
-    self.sha1 = util.hash_bower_component(
+    self.sha1 = bowerutil.hash_bower_component(
         hashlib.sha1(), os.path.dirname(bower_json_path)).hexdigest()
 
   def to_rule(self, packages):
@@ -106,6 +106,7 @@
 
 
 def build_bower_json(targets, buck_out):
+  """create bower.json so 'bower install' fetches transitive deps"""
   bower_json = collections.OrderedDict()
   bower_json['name'] = 'bower2buck-output'
   bower_json['version'] = '0.0.0'
@@ -117,6 +118,9 @@
       ['buck', 'query', '-v', '0',
        "filter('__download_bower', deps(%s))" % '+'.join(targets)],
       env=BUCK_ENV)
+
+  # __bower_version contains the version number coming from version
+  # attr in BUCK/BUILD
   deps = deps.replace('__download_bower', '__bower_version').split()
   subprocess.check_call(['buck', 'build'] + deps, env=BUCK_ENV)
 
diff --git a/tools/js/bowerutil.py b/tools/js/bowerutil.py
new file mode 100644
index 0000000..eb8893b
--- /dev/null
+++ b/tools/js/bowerutil.py
@@ -0,0 +1,47 @@
+# Copyright (C) 2013 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+from os import path
+
+
+def hash_bower_component(hash_obj, path):
+  """Hash the contents of a bower component directory.
+
+  This is a stable hash of a directory downloaded with `bower install`, minus
+  the .bower.json file, which is autogenerated each time by bower. Used in lieu
+  of hashing a zipfile of the contents, since zipfiles are difficult to hash in
+  a stable manner.
+
+  Args:
+    hash_obj: an open hash object, e.g. hashlib.sha1().
+    path: path to the directory to hash.
+
+  Returns:
+    The passed-in hash_obj.
+  """
+  if not os.path.isdir(path):
+    raise ValueError('Not a directory: %s' % path)
+
+  path = os.path.abspath(path)
+  for root, dirs, files in os.walk(path):
+    dirs.sort()
+    for f in sorted(files):
+      if f == '.bower.json':
+        continue
+      p = os.path.join(root, f)
+      hash_obj.update(p[len(path)+1:])
+      hash_obj.update(open(p).read())
+
+  return hash_obj
diff --git a/tools/js/download_bower.py b/tools/js/download_bower.py
old mode 100644
new mode 100755
index bcc417c..f5b7bf5
--- a/tools/js/download_bower.py
+++ b/tools/js/download_bower.py
@@ -23,8 +23,7 @@
 import subprocess
 import sys
 
-from tools import util
-
+import bowerutil
 
 CACHE_DIR = os.path.expanduser(os.path.join(
     '~', '.gerritcodereview', 'buck-cache', 'downloaded-artifacts'))
@@ -39,16 +38,20 @@
 def bower_info(bower, name, package, version):
   cmd = bower_cmd(bower, '-l=error', '-j',
                   'info', '%s#%s' % (package, version))
-  p = subprocess.Popen(cmd , stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+  try:
+    p = subprocess.Popen(cmd , stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+  except:
+    sys.stderr.write("error executing: %s\n" % ' '.join(cmd))
+    raise
   out, err = p.communicate()
   if p.returncode:
     sys.stderr.write(err)
-    raise OSError('Command failed: %s' % cmd)
+    raise OSError('Command failed: %s' % ' '.join(cmd))
 
   try:
     info = json.loads(out)
   except ValueError:
-    raise ValueError('invalid JSON from %s:\n%s' % (cmd, out))
+    raise ValueError('invalid JSON from %s:\n%s' % (" ".join(cmd), out))
   info_name = info.get('name')
   if info_name != name:
     raise ValueError('expected package name %s, got: %s' % (name, info_name))
@@ -82,7 +85,11 @@
   opts.add_option('-v', help='version number')
   opts.add_option('-s', help='expected content sha1')
   opts.add_option('-o', help='output file location')
-  opts, _ = opts.parse_args()
+  opts, args_ = opts.parse_args(args)
+
+  assert opts.p
+  assert opts.v
+  assert opts.n
 
   cwd = os.getcwd()
   outzip = os.path.join(cwd, opts.o)
@@ -100,7 +107,7 @@
 
     if opts.s:
       path = os.path.join(bc, opts.n)
-      sha1 = util.hash_bower_component(hashlib.sha1(), path).hexdigest()
+      sha1 = bowerutil.hash_bower_component(hashlib.sha1(), path).hexdigest()
       if opts.s != sha1:
         print((
           '%s#%s:\n'
diff --git a/tools/js/run_npm_binary.py b/tools/js/run_npm_binary.py
index d76eff5..d769b98 100644
--- a/tools/js/run_npm_binary.py
+++ b/tools/js/run_npm_binary.py
@@ -25,8 +25,6 @@
 import tarfile
 import tempfile
 
-from tools import util
-
 
 def extract(path, outdir, bin):
   if os.path.exists(os.path.join(outdir, bin)):
@@ -59,19 +57,21 @@
     # finished.
     extract_one(tar.getmember(bin))
 
-
 def main(args):
   path = args[0]
   suffix = '.npm_binary.tgz'
   tgz = os.path.basename(path)
+
   parts = tgz[:-len(suffix)].split('@')
 
   if not tgz.endswith(suffix) or len(parts) != 2:
     print('usage: %s <path/to/npm_binary>' % sys.argv[0], file=sys.stderr)
     return 1
 
-  name, version = parts
-  sha1 = util.hash_file(hashlib.sha1(), path).hexdigest()
+  name, _ = parts
+
+  # Avoid importing from gerrit because we don't want to depend on the right CWD.
+  sha1 = hashlib.sha1(open(path, 'rb').read()).hexdigest()
   outdir = '%s-%s' % (path[:-len(suffix)], sha1)
   rel_bin = os.path.join('package', 'bin', name)
   bin = os.path.join(outdir, rel_bin)