This is a pre-req to removing the dependency from RunLoop->MessageLoop
as many files only include run_loop.h but instantiate a MessageLoop.

The following fix script was applied to each file in the codebase
(plus a few hand fixes for DEPS and for //base):

def Fix(file_path):
  content = refactor_lib.ReadFile(file_path)

  # Assume fwd-decls are correct in first pass.
  if 'class MessageLoop;' in content:
    return False
  if 'class MessageLoopForUI;' in content:
    return False
  if 'class MessageLoopForIO;' in content:
    return False

  # Using base:: prefix ensures we don't match fwd-decls and other things.
  # Will require a few fixups for missing includes in //base proper.
  # Complex prefix in regex attempts to skip comments.
  matches = re.compile(r'(\n *[^/\n][^/\n][^/\n]*base::MessageLoop(ForUI|ForIO)?\b[^*])', re.DOTALL).findall(content)

  if not matches:
    return False

  # Ignore unique pointers in headers in first pass...
  if os.path.splitext(file_path)[1] == '.h':
    found = False
    for match in matches:
      if not 'std::unique_ptr<base::MessageLoop' in match[0]:
        found = True
        break
    if not found:
      return False

  updated_content = refactor_lib.AddInclude(file_path, content, "base/message_loop/message_loop.h")

  if updated_content == content:
    return False

  # Write updated file
  refactor_lib.WriteFile(file_path, updated_content)

  return True

TBR=gab@chromium.org
BUG=703346
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.android:android_cronet_tester;master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel

Review-Url: https://codereview.chromium.org/2876013002
Cr-Commit-Position: refs/heads/master@{#471412}