chromeos: Move several power-related classes to Ash.

Move SuspendObserver, UserActivityNotifier, and
VideoActivityNotifier from chrome/browser/chromeos/power to
ash/system/chromeos/power.

BUG=none

Review URL: https://codereview.chromium.org/25996007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227544 0039d316-1c4b-4281-b951-d872f2087c98
clang update script: clobber .dylibs

For Mac/ASan builds, a .dylib file containing ASan runtime functions is
copied into the build directory from LLVM. To make sure that the .dylib
file is updated when Clang is updated, we clobber all .dylib files in
the build directory, similarly to how we clobber .o files.

BUG=304125

Review URL: https://codereview.chromium.org/26424002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@227545 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 227545