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This CL adds conditions to the create/remove symlink rules for the
Windows installer which will cause the symlink to be created on install
and removed when either the MSI is being removed or being upgraded, but
not when the same version is re-run.

Change-Id: I7d9bbb24312ab9ad42c18d87528f1cdb9e4b5735
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031136Reviewed-by: Jamie Walch <jamiewalch@chromium.org>
Commit-Queue: Joe Downing <joedow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736915}