This cleans up a number of unnecessary differences in the LICENSE files:
- Removes C++ comments ("// ") from the beginnings of all the lines in license files that had them.
- Standardizes on having a blank line after the copyright line.
- Standardizes on having the final newline in the file.
- Standardizes on the indentation of the bulleted conditions.
- Standardizes on the locations of line breaks (re-wrapping the text)
This makes the license bodies--not including the copyright line--in almost all files the same, and matches the exact formatting already used in flutter/flutter and flutter/engine.
The only remaining non-copyright-line differences should now be:
- packages/image_picker/image_picker/LICENSE has an extra license
- packages/google_sign_in/extension_google_sign_in_as_googleapis_auth/LICENSE use "Google LLC" rather than "Google Inc." in the third condition.
Introduce the first version of the `extension_google_sign_in_as_googleapis_auth` package.
This package lets users of the `google_sign_in` plugin to create an authenticated HTTP clients (from `googleapis_auth`) that can access any APIs from the `googleapis` package.
