Add a new error type for added abstract methods.

If an abstract class that was released in prior version has an abstract
method added to it, this should be considered a breaking change since it
will break source compatibility.

Test: m -j12 and see the build break because of methods added to
ViewStructure

Change-Id: I28c7051a574bb50d2bde0c8034056add58ff69e5
2 files changed