Remove Xlib dependency in chromium_impl/ui

Remove Xlib dependency in chromium_impl/ui

We remove Xlib dependency, or rely on ecore-x instead.

We stop implementing ScreenEfl::GetCursorScreenPoint and
ScreenEfl::GetWindowUnderCursor.
Those methods are only used with toolkit view, which is not enabled for
our port. Those methods are also left unimplemented in android or ios.

In ScreenEfl::GetPrimaryDisplay, we use ecore-x methods instead of X11
methods.

In MakeWebKeyboardEvent, we hardcode all windowsKeyCode results, as is
currently done in quicksilver. This method is fragile, and won't work
currently on all layout keyboards. But it will still give better
results than the current behavior (where most keys are discarded, and
result in a 0 keyCode).

Additionally, we also set event.modifiers, which also used to implement
KeyBoardEvent.location.
Reviewed by: Antonio Gomes, Piotr Tworek

Change-Id: I1763ed7e43b2f216916abf75be56d0ca9ba2a84c
Signed-off-by: Arnaud Renevier <a.renevier@samsung.com>