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Interfaces are base classes that only consist of virtual methods. This
CL adds the following:
* deleted copy constructor and assignment - prevent unintended slicing
* protected constructors - prevent unintended direct instantiation
* protected destructors - prohibit the user of an interface
  implementation from destructing the implementation, enforcing that
  the user does not own the implementation

Change-Id: I2bb093e430cacb870846c74397051917ce50c83e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1663462
Commit-Queue: Victor Costan <pwnall@chromium.org>
Auto-Submit: Victor Costan <pwnall@chromium.org>
Reviewed-by: Staphany Park <staphany@chromium.org>
Cr-Commit-Position: refs/heads/master@{#670255}