This removes all chromium dependencies from media/base/ and completes
the build system in CMake.
The ClosureThread class and its classes were removed, as they were
specific to chromium base. ClosureThread has been replaced by
std::thread.
The byte-swapping utilities in network_util.cc have been removed and
replaced with absl.
generate_unique_temp_path() was split out of file_unittest.cc into
file_test_util.cc, where other test suites could make use of it.
WARN_UNUSED_RESULT was replaced with the C++ standard attribute
[[nodiscard]].
The base::Clock interface was replaced with a typedef for a function
pointer that returns the current time.
This re-enables the tests in http_key_fetcher_unittest.cc by using
httpbin.org.
Issue #1047 (CMake porting)
Issue #346 (absl porting)
This does not depend on absl, which frees macros.h from any library deps
that would make the CMake dependency tree more complicated. This also
fixes build errors in some environments.
Joey Parrish
KongQun Yang