Slightly improve exception messages for IDBCursor.

BUG=270033
R=jsbell@chromium.org

Review URL: https://codereview.chromium.org/24719002

git-svn-id: svn://svn.chromium.org/blink/trunk@159018 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Update mouse cursor on style changes without emitting fake mousemove event

BUG=228496

Review URL: https://codereview.chromium.org/25872002

git-svn-id: svn://svn.chromium.org/blink/trunk@159019 bbb929c8-8fbe-4397-9dbb-9b2b20218538