Add some suppressions for generated visual studio files to .gitignore.

R=scottmg@chromium.org, thakis@chromium.org
BUG=

Review URL: https://chromiumcodereview.appspot.com/22825022

git-svn-id: svn://svn.chromium.org/blink/trunk@156889 bbb929c8-8fbe-4397-9dbb-9b2b20218538