[ Merge of http://go/wvgerrit/85503 ]
Replacing a few instances of C's NULL with C++'s nullptr in some of the
smaller sub-directories in the CDM.
Note that clang-format has performed additional changes to some of the
test files that have not yet been formatted.
Bug: 120602075
Test: Android unittest
Change-Id: I926135ed4b85e9d2d58a014b4a62098b0cb7a373