Update tree walking to not update a list while iterating over it.

tools/checkdeps/java_checker.py

 # Copyright (c) 2012 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.
 
 """Checks Java files for illegal imports."""
 
 import codecs
 import os
 import re
 
@@ skipping 21 matching lines @@
   """
 
   EXTENSIONS = ['.java']
 
   def __init__(self, base_directory, verbose):
     self._base_directory = base_directory
     self._verbose = verbose
     self._classmap = {}
     self._PrescanFiles()
 
+  def _IgnoreDir(self, d):
+    # Skip hidden directories.
+    if d.startswith('.'):
+      return True
+    # Skip the "out" directory, as dealing with generated files is awkward.
+    # We don't want paths like "out/Release/lib.java" in our DEPS files.
+    # TODO(husky): We need some way of determining the "real" path to
+    # a generated file -- i.e., where it would be in source control if
+    # it weren't generated.
+    if d == 'out':
+      return True
+    # Skip third-party directories.
+    if d in ('third_party', 'ThirdParty'):
+      return True
+    return False
+
   def _PrescanFiles(self):
     for root, dirs, files in os.walk(self._base_directory):
       # Skip unwanted subdirectories. TODO(husky): it would be better to do
       # this via the skip_child_includes flag in DEPS files. Maybe hoist this
       # prescan logic into checkdeps.py itself?
-      for d in dirs:
-        # Skip hidden directories.
-        if d.startswith('.'):
-          dirs.remove(d)
-        # Skip the "out" directory, as dealing with generated files is awkward.
-        # We don't want paths like "out/Release/lib.java" in our DEPS files.
-        # TODO(husky): We need some way of determining the "real" path to
-        # a generated file -- i.e., where it would be in source control if
-        # it weren't generated.
-        if d == 'out':
-          dirs.remove(d)
-        # Skip third-party directories.
-        if d in ('third_party', 'ThirdParty'):
-          dirs.remove(d)
+      dirs[:] = [d for d in dirs if not self._IgnoreDir(d)]
       for f in files:
         if f.endswith('.java'):
           self._PrescanFile(os.path.join(root, f))
 
   def _PrescanFile(self, filepath):
     if self._verbose:
       print 'Prescanning: ' + filepath
     with codecs.open(filepath, encoding='utf-8') as f:
       short_class_name, _ = os.path.splitext(os.path.basename(filepath))
       for line in f:
@@ skipping 27 matching lines @@
           include_path = include_path.replace(os.path.sep, '/')
           rule = rules.RuleApplyingTo(include_path, filepath)
           if rule.allow == Rule.DISALLOW:
             dependee_status.AddViolation(
                 results.DependencyViolation(include_path, rule, rules))
         if '{' in line:
           # This is code, so we're finished reading imports for this file.
           break
 
     return dependee_status