Merge 102569 - Fix in-use updates for Chrome Frame.

Merge 102569 - Fix in-use updates for Chrome Frame.

On in-use updates, make a copy of the old chrome launcher's IE low rights elevation policy prior to registering the new npchrome_frame.dll so that running instances of IE can still launch Chrome.

In so doing, I also removed elevation policy addition/removal code from the installer so that npchrome_frame.dll's {un,}registration code is the one and only place where this is done.

BUG=95810
TEST=Install a previous version of GCF, run IE and visit some page that activates GCF, update to a version of GCF containing this fix, then try to visit another page that will activate GCF.  If all goes well, you won't see an IE security prompt.

Review URL: http://codereview.chromium.org/7976045

TBR=grt@chromium.org
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=104345