Add a snapshot of flutter/engine/src/build to our sdk

build/android/pylib/flag_changer.py

Index: build/android/pylib/flag_changer.py
diff --git a/build/android/pylib/flag_changer.py b/build/android/pylib/flag_changer.py
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+++ b/build/android/pylib/flag_changer.py
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+# 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
+
+import pylib.android_commands
+import pylib.device.device_utils
+
+from pylib.device import device_errors
+
+
+class FlagChanger(object):
+  """Changes the flags Chrome runs with.
+
+  There are two different use cases for this file:
+  * Flags are permanently set by calling Set().
+  * 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.
+    """
+    # TODO(jbudorick) Remove once telemetry switches over.
+    if isinstance(device, pylib.android_commands.AndroidCommands):
+      device = pylib.device.device_utils.DeviceUtils(device)
+    self._device = device
+    self._cmdline_file = cmdline_file
+
+    # Save the original flags.
+    try:
+      self._orig_line = self._device.ReadFile(self._cmdline_file).strip()
+    except device_errors.CommandFailedError:
+      self._orig_line = ''
+
+    # Parse out the flags into a list to facilitate adding and removing flags.
+    self._current_flags = self._TokenizeFlags(self._orig_line)
+
+  def Get(self):
+    """Returns list of current flags."""
+    return self._current_flags
+
+  def Set(self, flags):
+    """Replaces all flags on the current command line with the flags given.
+
+    Args:
+      flags: A list of flags to set, eg. ['--single-process'].
+    """
+    if flags:
+      assert flags[0] != 'chrome'
+
+    self._current_flags = flags
+    self._UpdateCommandLineFile()
+
+  def AddFlags(self, flags):
+    """Appends flags to the command line if they aren't already there.
+
+    Args:
+      flags: A list of flags to add on, eg. ['--single-process'].
+    """
+    if flags:
+      assert flags[0] != 'chrome'
+
+    # Avoid appending flags that are already present.
+    for flag in flags:
+      if flag not in self._current_flags:
+        self._current_flags.append(flag)
+    self._UpdateCommandLineFile()
+
+  def RemoveFlags(self, flags):
+    """Removes flags from the command line, if they exist.
+
+    Args:
+      flags: 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.
+    """
+    if flags:
+      assert flags[0] != 'chrome'
+
+    for flag in flags:
+      if flag in self._current_flags:
+        self._current_flags.remove(flag)
+    self._UpdateCommandLineFile()
+
+  def Restore(self):
+    """Restores the flags to their original state."""
+    self._current_flags = self._TokenizeFlags(self._orig_line)
+    self._UpdateCommandLineFile()
+
+  def _UpdateCommandLineFile(self):
+    """Writes out the command line to the file, or removes it if empty."""
+    logging.info('Current flags: %s', self._current_flags)
+    # Root is not required to write to /data/local/tmp/.
+    use_root = '/data/local/tmp/' not in self._cmdline_file
+    if self._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(['_'] + self._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:]