Pull out flow control functionality from ReliableQuicStream into a new

Pull out flow control functionality from ReliableQuicStream into a new
class, QuicFlowController.

Without this refactoring, all the accounting of bytes
sent/buffered/consumed, comparisons of these with limits to decide if
blocked or not, will be duplicated in ReliableQuicStream and
QuicConnection. Putting all this in a new class means it's easier to
have more comprehensive testing, simplifies ReliableQuicStream, and will
make it much easier to add Connection level flow control (work in
progress internal change: 63944402).

Refactor of QUIC stream flow control. No behavior change, still
protected behind FLAGS_enable_quic_stream_flow_control. This flag is
currently disabled.

Merge internal change: 64733866

R=rch@chromium.org

[ramant (doing other things), 2014-04-18 02:04:22]

On 2014/04/18 01:23:35, ramant wrote:

Hi Ryan,
  IMO, because flow control is disabled in chromium, this CL shouldn't break
QUIC.

[ramant (doing other things), 2014-04-18 02:45:20]

On 2014/04/18 02:04:22, ramant wrote:
> On 2014/04/18 01:23:35, ramant wrote:
> 
> Hi Ryan,
>   IMO, because flow control is disabled in chromium, this CL shouldn't break
> QUIC.

Ported Robbie Shade's CL to disable flow control. Thought the flags disabled
flow control, but I was wrong.

[ramant (doing other things), 2014-04-18 02:46:16]

On 2014/04/18 02:45:20, ramant wrote:
> On 2014/04/18 02:04:22, ramant wrote:
> > On 2014/04/18 01:23:35, ramant wrote:
> > 
> > Hi Ryan,
> >   IMO, because flow control is disabled in chromium, this CL shouldn't break
> > QUIC.
> 
> Ported Robbie Shade's CL to disable flow control. Thought the flags disabled
> flow control, but I was wrong.

https://codereview.chromium.org/242583002/ disabled flow control for QUIC
versions < 17.

[Ryan Hamilton, 2014-04-18 03:39:53]

lgtm