Use Google3 naming style to match new
projects' and open source google projects' style.
Preferred to do this in a massive CL so as to avoid
style inconsistencies that plague legacy code bases.
This is a relatively NEW code base, may as well keep
it up to date.
Test: name/style refactor - existing tests pass
Change-Id: Ie80ecb78d46ec53efdfca2336bb57d96cbb7fb87
file::mkdirs would try to extract the first part of the
path '/path' which would be the empty string ''. Mkdir would
fail creating the empty string directory.
Change-Id: Ice8ba92135f145f52f3663499a2c49eebe797328