Use flag_changer in catapult devil.android

This CL updates the dependency on pylib.flag_changer to
Catapult's devil.android.flag_changer in Chromium repo.

- The previous CL added devil.android.flag_changer in
catapult: https://crrev.com/1675773002/
- The next CL will remove pylib.flag_changer.

BUG=583785

Review URL: https://codereview.chromium.org/1677313002

Cr-Commit-Position: refs/heads/master@{#374936}

3 files changed, 177 insertions, 2 deletions

diff --git a/build/android/devil/android/flag_changer.py b/build/android/devil/android/flag_changer.py
new file mode 100644
index 0000000..5b9021f
--- /dev/null
+++ b/build/android/devil/android/flag_changer.py
@@ -0,0 +1,175 @@
+# 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.
+
+import logging
+
+from devil.android import device_errors
+
+
+class FlagChanger(object):
+  """Changes the flags Chrome runs with.
+
+    Flags can be temporarily set for a particular set of unit tests.  These
+    tests should call Restore() to revert the flags to their original state
+    once the tests have completed.
+  """
+
+  def __init__(self, device, cmdline_file):
+    """Initializes the FlagChanger and records the original arguments.
+
+    Args:
+      device: A DeviceUtils instance.
+      cmdline_file: Path to the command line file on the device.
+    """
+    self._device = device
+    self._cmdline_file = cmdline_file
+
+    stored_flags = ''
+    if self._device.PathExists(self._cmdline_file):
+      try:
+        stored_flags = self._device.ReadFile(self._cmdline_file).strip()
+      except device_errors.CommandFailedError:
+        pass
+    # Store the flags as a set to facilitate adding and removing flags.
+    self._state_stack = [set(self._TokenizeFlags(stored_flags))]
+
+  def ReplaceFlags(self, flags):
+    """Replaces the flags in the command line with the ones provided.
+       Saves the current flags state on the stack, so a call to Restore will
+       change the state back to the one preceeding the call to ReplaceFlags.
+
+    Args:
+      flags: A sequence of command line flags to set, eg. ['--single-process'].
+             Note: this should include flags only, not the name of a command
+             to run (ie. there is no need to start the sequence with 'chrome').
+    """
+    new_flags = set(flags)
+    self._state_stack.append(new_flags)
+    self._UpdateCommandLineFile()
+
+  def AddFlags(self, flags):
+    """Appends flags to the command line if they aren't already there.
+       Saves the current flags state on the stack, so a call to Restore will
+       change the state back to the one preceeding the call to AddFlags.
+
+    Args:
+      flags: A sequence of flags to add on, eg. ['--single-process'].
+    """
+    self.PushFlags(add=flags)
+
+  def RemoveFlags(self, flags):
+    """Removes flags from the command line, if they exist.
+       Saves the current flags state on the stack, so a call to Restore will
+       change the state back to the one preceeding the call to RemoveFlags.
+
+       Note that calling RemoveFlags after AddFlags will result in having
+       two nested states.
+
+    Args:
+      flags: A sequence of flags to remove, eg. ['--single-process'].  Note
+             that we expect a complete match when removing flags; if you want
+             to remove a switch with a value, you must use the exact string
+             used to add it in the first place.
+    """
+    self.PushFlags(remove=flags)
+
+  def PushFlags(self, add=None, remove=None):
+    """Appends and removes flags to/from the command line if they aren't already
+       there. Saves the current flags state on the stack, so a call to Restore
+       will change the state back to the one preceeding the call to PushFlags.
+
+    Args:
+      add: A list of flags to add on, eg. ['--single-process'].
+      remove: A list of flags to remove, eg. ['--single-process'].  Note that we
+              expect a complete match when removing flags; if you want to remove
+              a switch with a value, you must use the exact string used to add
+              it in the first place.
+    """
+    new_flags = self._state_stack[-1].copy()
+    if add:
+      new_flags.update(add)
+    if remove:
+      new_flags.difference_update(remove)
+    self.ReplaceFlags(new_flags)
+
+  def Restore(self):
+    """Restores the flags to their state prior to the last AddFlags or
+       RemoveFlags call.
+    """
+    # The initial state must always remain on the stack.
+    assert len(self._state_stack) > 1, (
+      "Mismatch between calls to Add/RemoveFlags and Restore")
+    self._state_stack.pop()
+    self._UpdateCommandLineFile()
+
+  def _UpdateCommandLineFile(self):
+    """Writes out the command line to the file, or removes it if empty."""
+    current_flags = list(self._state_stack[-1])
+    logging.info('Current flags: %s', current_flags)
+    # Root is not required to write to /data/local/tmp/.
+    use_root = '/data/local/tmp/' not in self._cmdline_file
+    if current_flags:
+      # The first command line argument doesn't matter as we are not actually
+      # launching the chrome executable using this command line.
+      cmd_line = ' '.join(['_'] + current_flags)
+      self._device.WriteFile(
+          self._cmdline_file, cmd_line, as_root=use_root)
+      file_contents = self._device.ReadFile(
+          self._cmdline_file, as_root=use_root).rstrip()
+      assert file_contents == cmd_line, (
+          'Failed to set the command line file at %s' % self._cmdline_file)
+    else:
+      self._device.RunShellCommand('rm ' + self._cmdline_file,
+                                   as_root=use_root)
+      assert not self._device.FileExists(self._cmdline_file), (
+          'Failed to remove the command line file at %s' % self._cmdline_file)
+
+  @staticmethod
+  def _TokenizeFlags(line):
+    """Changes the string containing the command line into a list of flags.
+
+    Follows similar logic to CommandLine.java::tokenizeQuotedArguments:
+    * Flags are split using whitespace, unless the whitespace is within a
+      pair of quotation marks.
+    * Unlike the Java version, we keep the quotation marks around switch
+      values since we need them to re-create the file when new flags are
+      appended.
+
+    Args:
+      line: A string containing the entire command line.  The first token is
+            assumed to be the program name.
+    """
+    if not line:
+      return []
+
+    tokenized_flags = []
+    current_flag = ""
+    within_quotations = False
+
+    # Move through the string character by character and build up each flag
+    # along the way.
+    for c in line.strip():
+      if c is '"':
+        if len(current_flag) > 0 and current_flag[-1] == '\\':
+          # Last char was a backslash; pop it, and treat this " as a literal.
+          current_flag = current_flag[0:-1] + '"'
+        else:
+          within_quotations = not within_quotations
+          current_flag += c
+      elif not within_quotations and (c is ' ' or c is '\t'):
+        if current_flag is not "":
+          tokenized_flags.append(current_flag)
+          current_flag = ""
+      else:
+        current_flag += c
+
+    # Tack on the last flag.
+    if not current_flag:
+      if within_quotations:
+        logging.warn('Unterminated quoted argument: ' + line)
+    else:
+      tokenized_flags.append(current_flag)
+
+    # Return everything but the program name.
+    return tokenized_flags[1:]
diff --git a/build/android/pylib/instrumentation/test_runner.py b/build/android/pylib/instrumentation/test_runner.py
index 795e817..79e7d6d 100644
--- a/build/android/pylib/instrumentation/test_runner.py
+++ b/build/android/pylib/instrumentation/test_runner.py
@@ -11,8 +11,8 @@ import re
 import time
 
 from devil.android import device_errors
+from devil.android import flag_changer
 from pylib import constants
-from pylib import flag_changer
 from pylib import valgrind_tools
 from pylib.base import base_test_result
 from pylib.base import base_test_runner
diff --git a/build/android/pylib/local/device/local_device_instrumentation_test_run.py b/build/android/pylib/local/device/local_device_instrumentation_test_run.py
index ee8910a..9298d75 100644
--- a/build/android/pylib/local/device/local_device_instrumentation_test_run.py
+++ b/build/android/pylib/local/device/local_device_instrumentation_test_run.py
@@ -7,8 +7,8 @@ import re
 import time
 
 from devil.android import device_errors
+from devil.android import flag_changer
 from devil.utils import reraiser_thread
-from pylib import flag_changer
 from pylib import valgrind_tools
 from pylib.base import base_test_result
 from pylib.local.device import local_device_test_run