Make the update installer fail when attempting to install a 64-bit-only update
on a 32-bit-only system.

The server infrastructure should not deliver 64-bit-only updates to
32-bit-only systems, but this depends on the new -32bit tag suffix support
already being on the system prior to the attempted delivery of a 64-bit-only
update. The update installer will now sanity-check this, and if the system
will not be capable of running the updated version, it will exit before
attempting to install it. Additionally, it will set the -32bit tag suffix so
that during a subsequent update check, the server should deliver the proper
32-bit-only update (likely the final 32-bit version), or no update at all.

This also serves as a failsafe against breaking users on 32-bit-only systems
if the server-side -32bit tag suffix detection isn't working properly.

BUG=18323,303280
R=thakis@chromium.org, thakis

Review URL: https://codereview.chromium.org/124813002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@243088 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 243088