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Replace the SetSubclassProperties method with CheckSubclassProperties,
which checks the properties that were set, and checks that all others
are the default values.

The next step is to delete all of the sub-classes (including the
just-added CheckSubclassProperties functions).

BUG=667966
CQ_INCLUDE_TRYBOTS=master.tryserver.blink:linux_trusty_blink_rel

Review-Url: https://codereview.chromium.org/2628713002
Cr-Commit-Position: refs/heads/master@{#443029}