Remove use of WebInputEventFactory in EventSender.
* Removes EventSender::DispatchMessage, which does not seem to be used.
(No layout test seems to invoke this method.)
* Gathers isSystemKey logic. The Windows-specific F10 logic existed
in the testing, but not production, code, so it was removed.
* Removes key_code_mapping.h. The Mac logic needs the key codes for
VKEY_B and VKEY_I, which are not in this file. Further investigation reveals
that this file is a subset of the constants in ui/events/keycodes/keyboard_codes.h.
It seems legal to include that from content/, so that header is used instead.
BUG=363455
Review URL: https://codereview.chromium.org/
237963015
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@264611 0039d316-1c4b-4281-b951-d872f2087c98