8583 Pipe Z bounds from ViewportMetrics to Flow (cla: yes)

8585 Check that TransformLayer has a finite matrix (cla: yes)

8591 Glitchiness with Tab Characters (cla: yes)

8592 Variant type for C++ client wrapper (cla: yes)

8593 Roll buildroot to ce7b5c786a12927c9e0b4543af267d48c52e0b3a (cla: yes)

8594 Enable VM service authentication codes by default (cla: yes)

8598 Implement StandardMethodCodec for C++ shells (cla: yes)

8600 Add desktop shell unittests to test script (cla: yes)

8605 Allow building without python2 (cla: yes)