x11: Simplify some more event-rewrite code.

The WindowTreeHost implementation for X11 currently receives an event from X11
when the keyboard mapping changes in the system. The implementation then calls
into WindowTreeHost::OnKeyboardMappingChanged(), which triggers the
corresponding method in all WindowTreeHostObservers. The EventRewriter is a
WindowTreeHostObserver, and so it can then reset the keycodes it maintains.

But the EventRewriter is also a MessagePumpObserver, which means it already
receives the X11 MappingNotify event, and so the plumbing of the event through
aura is unnecessary.  There is no other consumer of
WindowTreeHostObserver::OnKeyboardMappingChanged(), so remove it from the api.

BUG=343639
R=oshima@chromium.org, sky@chromium.org

Review URL: https://codereview.chromium.org/183893031

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255185 0039d316-1c4b-4281-b951-d872f2087c98
Fix reference builds on mac.

TBR=isherman@chromium.org,qyearsley@chromium.org
NOTRY=True
BUG=

Review URL: https://codereview.chromium.org/181233013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255186 0039d316-1c4b-4281-b951-d872f2087c98
Compatibility fix for arm64 on iOS

Manually patches in 77400c22b5bafd8aaaa75f90a1d997838204577a from upstream.

Description:
  Also on arm64, BOOL seems to be encoded as "bool" (the 'B' objcType, or
  _C_BOOL) rather than the historical 'c', but NSValue can still use 'c',
  so we need to have those compare as equal.

BUG=314720

Review URL: https://codereview.chromium.org/177373009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255187 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255188 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255188