Verify java.io.{CharArrayReader,StringBufferInputStream}.

CL [1] backported a fix from OpenJDK9b132 (this fix has also
been backported to OpenJDK8u152) but erroneously stated that
the fix was from openJdk80u112.

Since the current upstream for these files is only OpenJDK 8u121-b13,
the fix currently still needs change markers; these can be
removed once the files are updated beyond OpenJDK8u152.

[1] http://r.android.com/330889 commit a810284b
Bug: 31028374
Bug: 35910877
Test: Treehugger
Test: tools/upstream/upstream-diff java.io.{CharArrayReader,StringBufferInputStream}

Change-Id: I9846985455b49095f117560f533e78af95d487c5