Pool 64 bits of entropy instead of calling OpenSSL's RNG for one bit

Pool 64 bits of entropy instead of calling OpenSSL's RNG for one bit
when creating packets. Clean up the entropy bit while I'm at it.

Changes:

1. QuicPacketCreator buffers 64 bits of entropy and consumes them
   one-at-a-time. This should resolve the performance issue. Covered
   this with a unit test. Removed the RandBool call from QuicRandom.

2. The first packet gets a random entropy bit. We used to never set it
   because we failed to test it properly. This was sad because the first
   packet deserves the most protection.

3. The entropy hash computation had a TODO to make it stronger, but I'm
   convinced the current algorithm is in fact sound. Removed the TODO
   and tightened up the implementation to avoid an unpredictable branch
   (no behavior change!) Also covered by the test.

4. Fixed the bugs in QuicConnectionTest that prevented setting the bit
   in the first packet. Switched tests to properly use MockRandom.

Merge internal change: 57908681

R=rch@chromium.org

[Ryan Hamilton, 2013-12-12 22:43:33]

lgtm, modulo one question.

https://codereview.chromium.org/109323006/diff/1/net/quic/quic_http_stream_te...
File net/quic/quic_http_stream_test.cc (right):

https://codereview.chromium.org/109323006/diff/1/net/quic/quic_http_stream_te...
net/quic/quic_http_stream_test.cc:136: random_generator_(0),
Do we need 2 MockRandoms?

[ramant (doing other things), 2013-12-12 22:53:47]

https://codereview.chromium.org/109323006/diff/1/net/quic/quic_http_stream_te...
File net/quic/quic_http_stream_test.cc (right):

https://codereview.chromium.org/109323006/diff/1/net/quic/quic_http_stream_te...
net/quic/quic_http_stream_test.cc:136: random_generator_(0),
On 2013/12/12 22:43:33, Ryan Hamilton wrote:
> Do we need 2 MockRandoms?

Done.

[ramant (doing other things), 2013-12-12 23:00:10]

https://codereview.chromium.org/109323006/diff/1/net/quic/quic_http_stream_te...
File net/quic/quic_http_stream_test.cc (right):

https://codereview.chromium.org/109323006/diff/1/net/quic/quic_http_stream_te...
net/quic/quic_http_stream_test.cc:136: random_generator_(0),
On 2013/12/12 22:43:33, Ryan Hamilton wrote:
> Do we need 2 MockRandoms?

I wasn't sure when I did the merge. Tested the code with one MockRandom and all
tests have passed. Deleted the public MockRandom. thanks.

[Ryan Hamilton, 2013-12-13 00:40:47]

On 2013/12/12 23:00:10, ramant wrote:
>
https://codereview.chromium.org/109323006/diff/1/net/quic/quic_http_stream_te...
> File net/quic/quic_http_stream_test.cc (right):
> 
>
https://codereview.chromium.org/109323006/diff/1/net/quic/quic_http_stream_te...
> net/quic/quic_http_stream_test.cc:136: random_generator_(0),
> On 2013/12/12 22:43:33, Ryan Hamilton wrote:
> > Do we need 2 MockRandoms?
> 
> I wasn't sure when I did the merge. Tested the code with one MockRandom and
all
> tests have passed. Deleted the public MockRandom. thanks.

lgtm