Remove redundant mapping of net errors to strings.
The new list does not have the leading "net::ERR_", to slightly reduce
the size of net when compiled. This reduces the size of libcronet.so
by about 8k, with symbols stripped.
Also add a function to get network error strings without the leading,
"net::" as a number of consumers were removing it with duplicated code.
This CL slight breaks NetLog loading functionality - loading old logs
in new versions will result in error codes missing the leading "ERR_",
and the other direction results in error codes having an extra leading
"ERR_".
BUG=399025
Review URL: https://codereview.chromium.org/
432553003
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@288065 0039d316-1c4b-4281-b951-d872f2087c98