Revert 143782 - Use a better registration suffix that will always be unique while respecting the MS…

Revert 143782 - Use a better registration suffix that will always be unique while respecting the MSDN rules. (Triggered assertion failures in browser_tests blocking WebKit rolls.)

The suffix will now be the base32 encoding of the md5 hash of the user's username. This is always unique and can be determined many times deterministically without I/O access (as opposed to other methods we considered).

It respects all MSDN constraint for properties onto which it is appended.

This replaces the prior-style username suffixes for new installs.

Old-style suffixes (i.e. unsuffixed and username suffixed) will however be kept as is through future updates.

Design doc: https://docs.google.com/a/chromium.org/document/d/1qmcV3uYBh3JwvXhYkI7asg0nN7KfVMWVOzND4p0jQ3E/edit

BUG=133810
TEST= http://goo.gl/ZZ7gE
installer_util_unittests.exe --gtest_filter=ShellUtilTest.*

Review URL: https://chromiumcodereview.appspot.com/10617002

TBR=gab@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=143833