Stop preemptively generating an RSA key pair.

RSA isn't used by the Java binding, it isn't the default for Obj-C,
and this identity store class isn't used at all by Chrome. So in most
cases, preemptively generating an RSA key pair just wastes CPU cycles
and blocks the worker thread.

If a native C++ application really wants to preemptively generate an RSA
key pair, it can easily do this by passing in its own DtlsIdentityStoreImpl
and calling GenerateIdentity on it.

R=juberti@chromium.org

Review URL: https://codereview.webrtc.org/1907083005 .

Cr-Original-Commit-Position: refs/heads/master@{#12498}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 9cb23a3579990ff78e3ceb6b6a88a06912662d7b
2 files changed