Applies non-functional changes from 7u40 - 8u60

These changes cover:
* JavaDoc improvements.
* Internal use of generics.
* Improve diagnostics for some internal errors.
* Add annotations, e.g. @Override, @SuppressWarnings where
  necessary.
* Formatting changes.
* Removing unnecessary modifiers, e.g. public on package private
  classes, final on private methods, etc.
* Copyright updates.

Bug: 29352743
Test: flashed onto device and made sure that it comes up
properly, ran make docs and checked the output of a few
representative changes.
Change-Id: I731c556d7d4401e2d571ca9b2a69e63b29ef89e1