Merge from widevine of http://go/wvgerrit/14134
This CL adjusts the nonce flood test so that the timing is more
explicit. Also, if the test fails, the error message should tell us
exactly how many nonces were generated and the duration of the test.
Thus we'll be able to tell if the test almost passed.
b/19081206
Change-Id: I2c59755466b017910b86f6b02f2883a771d0ccb7