There is now a syscall for getting cryptographically secure random bytes. R=asiva@google.com Review URL: https://codereview.chromium.org/2204523002 .
Closes https://github.com/dart-lang/sdk/issues/26721 R=rmacnak@google.com Review URL: https://codereview.chromium.org/2081433002 .
BUG= R=chinmaygarde@google.com, rmacnak@google.com Review URL: https://codereview.chromium.org/1799933002 .
BUG= R=hausner@google.com Review URL: https://codereview.chromium.org/1497033003 .