[Android WebView] Allow copyright notices not to require a whitespace before

This allows the tool to detect copyrights in HTML files properly.
Corectness verified by manually comparing results before and after the change.

Other small changes:

  - sort copyrights found to make comparison more straightforward;

  - factor out the copyright regex into a variable, as otherwise I was bumping
    into 80 chars limit.

BUG=345835
NOTRY=true

Review URL: https://codereview.chromium.org/177633002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@252926 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 252926