Add a .clang-format file to give us local control over Blink style.

This also makes editor integration somewhat easier by letting editors pass just "-style=file -assume-filename=<filename>" to clang-format instead of needing to guess the desired style based on the path.

We could name this file _clang-format instead, if that's easier for Windows.

Review URL: https://codereview.chromium.org/32673005

git-svn-id: svn://svn.chromium.org/blink/trunk@160157 bbb929c8-8fbe-4397-9dbb-9b2b20218538