Factor out ParseRecord to handle dep record format

Add a function, ParseRecord, that parses a deps log record into an
intermediate data structure, InputRecord. This function consolidates
the deps record format handling in one place -- previously, the various
stages of DepsLog::Load each handled parts of the record format.

Test: ninja_test
Change-Id: Iaf5878b2d5a62c778526e049f1db07ba6a15d886
1 file changed