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This CL modifies clients that use URLRequest::Read() method
or implement net::Delegate/net::NetworkDelegate methods
and makes them to use returned networking errors instead,
which are returned in term of int.

Old implementation of URLRequest::Read() used to set its
status inside the URLRequest object itself and clients
used to check the status by calling request->status().

The main CL that changes URLRequest::Read and delegate
methods is here - https://codereview.chromium.org/2262653003

BUG=423484

Review-Url: https://codereview.chromium.org/2261103002
Cr-Commit-Position: refs/heads/master@{#419413}