Rename VideoCaptureDeviceImpl -> ContentVideoCaptureDeviceCore

The class in question isn't an implementation for a generic VideoCaptureDevice;
it's used just as the core of tab/desktop capture devices.  Rename it to
reflect function.

BUG=269312
TEST=local build on ChromeOS Linux

Review URL: https://codereview.chromium.org/159333003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250661 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250661
Linux Aura: Fix missing system borders on KDE and other window managers.

When a window with system borders does not have a custom shape, its
XShape is set to null, rather than being set to a rectangle the size of
the window. Several window managers (including KDE, XFCE and XMonad)
refuse to put a native window border on a window with a custom shape.

BUG=338916

Review URL: https://codereview.chromium.org/145973004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@250662 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 250662