Hide X11 dependencies when use_x11=0.

When using a non X11 build with Ozone, we still have dependencies on
X11. This patch tries to hide X11 and related dependencies when
use_x11=0

Review URL: https://codereview.chromium.org/148643002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251981 0039d316-1c4b-4281-b951-d872f2087c98
Refactor device scale factor on Mac and fix CoreAnimation bug

Rename some functions to be more meaningful:
- RWHVMac::scale_factor -> RWHVMac::ViewScaleFactor
- RWHVCocoa::deviceScaleFactor_ -> RWHVMac::backing_store_scale_factor
- ::ScaleFactor(NSView*) -> ScaleFactorForView(NSView*)

Move code to update the scale factor of the backing store from
being in RWHVCocoa::updateTabBackingStoreScaleFactor to be
in RWHVMac::UpdateBackingStoreScaleFactor.

Work around a bug where updating the contentsScale of a
CAOpenGLLayer that dynamically changes its isAsynchronous
property results in corruption by re-creating the CAOpenGLLayer
when a change in scale factor is detected.

BUG=245900

Review URL: https://codereview.chromium.org/171763002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@251982 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 251982