Polymer: Remove obsolete find_unused_elements.py script.

This script:
 - Is basically unmaintained.
 - It's unclear if it still works
 - Has not been very helpful and does not justify the cost of
   maintaining it.
 - Is unlikely to be ported to work with Polymer3 JS imports in
   third_party/polymer/v3_0/ folder.

Moreover, we have way less Polymer UI elemens dependencies than when
this script was originally authored, and manually identifying unused
elements has not been a problem.

Fixed: 997850
Change-Id: Ic062bf1bc1cccf4bd2c98bb37a83b9103270dbb2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2569372
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Auto-Submit: dpapad <dpapad@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833073}

third_party/polymer/v1_0/find_unused_elements.py

-# Copyright 2016 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-
-"""Identifies Polymer elements that downloaded but not used by Chrome.
-
-Only finds "first-order" unused elements; re-run after removing unused elements
-to check if other elements have become unused.
-"""
-
-import os
-import re
-import subprocess
-import sys
-
-_HERE_PATH = os.path.dirname(__file__)
-_SRC_PATH = os.path.normpath(os.path.join(_HERE_PATH, '..', '..', '..'))
-sys.path.append(os.path.join(_SRC_PATH, 'third_party', 'node'))
-import node
-import node_modules
-
-class UnusedElementsDetector(object):
-  """Finds unused Polymer elements."""
-
-  # Unused elements to ignore because we plan to use them soon.
-  __WHITELIST = (
-    # Necessary for closure.
-    'polymer-externs',
-    # Not used yet. Will be used as part of Polymer 2 migration.
-    'polymer2',
-    'shadycss',
-    # Not used yet. Will be used when pages are moved off of HTML imports.
-    'html-imports',
-  )
-
-  def __init__(self):
-    polymer_dir = os.path.dirname(os.path.realpath(__file__))
-    self.__COMPONENTS_DIR = os.path.join(polymer_dir, 'components-chromium')
-
-  @staticmethod
-  def __StripHtmlComments(filename):
-    """Returns the contents of an HTML file with <!-- --> comments stripped.
-
-    Not a real parser.
-
-    Args:
-      filename: The name of the file to read.
-
-    Returns:
-      A string consisting of the file contents with comments removed.
-    """
-    with open(filename) as f:
-      return re.sub('<!--.*?-->', '', f.read(), flags=re.MULTILINE | re.DOTALL)
-
-  @staticmethod
-  def __StripJsComments(filename):
-    """Returns the minified contents of a JavaScript file with comments and
-    grit directives removed.
-
-    Args:
-      filename: The name of the file to read.
-
-    Returns:
-      A string consisting of the minified file contents with comments and grit
-      directives removed.
-    """
-    with open(filename) as f:
-      text = f.read()
-    text = re.sub('<if .*?>', '', text, flags=re.IGNORECASE)
-    text = re.sub('</if>', '', text, flags=re.IGNORECASE)
-
-    return node.RunNode([node_modules.PathToTerser(), filename])
-
-  @staticmethod
-  def __StripComments(filename):
-    """Returns the contents of a JavaScript or HTML file with comments removed.
-
-    Args:
-      filename: The name of the file to read.
-
-    Returns:
-      A string consisting of the file contents processed via
-      __StripHtmlComments or __StripJsComments.
-    """
-    if filename.endswith('.html'):
-      text = UnusedElementsDetector.__StripHtmlComments(filename)
-    elif filename.endswith('.js'):
-      text = UnusedElementsDetector.__StripJsComments(filename)
-    else:
-      assert False, 'Invalid filename: %s' % filename
-    return text
-
-  def Run(self):
-    """Finds unused Polymer elements and prints a summary."""
-    proc = subprocess.Popen(
-      ['git', 'rev-parse', '--show-toplevel'],
-      stdout=subprocess.PIPE)
-    src_dir = proc.stdout.read().strip()
-
-    elements = []
-    for name in os.listdir(self.__COMPONENTS_DIR):
-      path = os.path.join(self.__COMPONENTS_DIR, name)
-      if os.path.isdir(path):
-        elements.append(name)
-
-    relevant_src_dirs = (
-      os.path.join(src_dir, 'chrome'),
-      os.path.join(src_dir, 'ui'),
-      os.path.join(src_dir, 'components'),
-      self.__COMPONENTS_DIR
-    )
-
-    unused_elements = []
-    for element in elements:
-      if (element not in self.__WHITELIST and
-          not self.__IsImported(element, relevant_src_dirs)):
-        unused_elements.append(element)
-
-    if unused_elements:
-      print 'Found unused elements: %s\nRemove from bower.json and re-run ' \
-        'reproduce.sh, or add to whitelist in %s' % (
-          ', '.join(unused_elements), os.path.basename(__file__))
-
-  def __IsImported(self, element_dir, dirs):
-    """Returns whether the element directory is used in HTML or JavaScript.
-
-    Args:
-      element_dir: The name of the element's directory.
-      dirs: The directories in which to check for usage.
-
-    Returns:
-      True if the element's directory is used in |dirs|.
-    """
-    for path in dirs:
-      # Find an import or script referencing the tag's directory.
-      for (dirpath, _, filenames) in os.walk(path):
-        # Ignore the element's own files.
-        if dirpath.startswith(os.path.join(
-            self.__COMPONENTS_DIR, element_dir)):
-          continue
-
-        for filename in filenames:
-          if not filename.endswith('.html') and not filename.endswith('.js'):
-            continue
-
-          with open(os.path.join(dirpath, filename)) as f:
-            text = f.read()
-          if not re.search('/%s/' % element_dir, text):
-            continue
-
-          # Check the file again, ignoring comments (e.g. example imports and
-          # scripts).
-          if re.search('/%s' % element_dir,
-                       self.__StripComments(
-                         os.path.join(dirpath, filename))):
-            return True
-    return False
-
-
-if __name__ == '__main__':
-  UnusedElementsDetector().Run()

third_party/polymer/v1_0/reproduce.sh

@@ -111,6 +111,3 @@ echo 'Creating GN files for interfaces and externs...'
 ./generate_gn.sh 2 # polymer_version=2
 
 popd > /dev/null
-
-echo 'Searching for unused elements...'
-python "$(dirname "$0")"/find_unused_elements.py

third_party/polymer/v3_0/reproduce.sh

@@ -95,5 +95,3 @@ python ../v1_0/rgbify_hex_vars.py --filter-prefix=google --replace \
 
 echo 'Creating GN files for interfaces and externs...'
 ../v1_0/generate_gn.sh 3 # polymer_version=3
-
-# TODO find unused elements?