cc: Added a spiral difference iterator to tiling data.

This patch adds another iterator to tiling data. This iterator acts
similar to the difference iterator, but it also takes an extra center
rect parameter. The indices are returned in a counter-clockwise spiral
around the center rect. Note that the center rect itself is also
considered to be ignored.

Added tests to verify the behavior. Currently, the iterator is not used
anywhere outside of the unit tests.

R=enne@chromium.org

Review URL: https://codereview.chromium.org/183123004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254622 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254622
Pass user gestures with chrome.tabs.executeScript.

BUG=340816
TEST=ExecuteScriptApiTest.UserGesture

Review URL: https://codereview.chromium.org/154893002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@254623 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 254623