ubsan doesn't like us incrementing std::string::npos, even if we won't use
the result.
Bug: http://b/28729303
Test: ran tests
Change-Id: I8227eca57dc6f3e49626c7025514caa04ef18f0a
Makes it easier to write correct code in a world where the maximum
property key/value lengths change.
Bug: http://b/23102347
Test: libbase_test64
Change-Id: I100f00904221bbcef9e8786a4e6e30428039bb49