UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/55.0.2883.95 Safari/537.36

Steps to reproduce the problem:
1. This is a bug reported by our static analysis tool.
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What is the expected behavior?

What went wrong?
In function QuicConsumedData QuicConnection::SendStreamData, a fast path is implemented to process packets which fit into a standard buffer and don't need padding. The fastpath function ConsumeDataFastPath then calls "CreateAndSerializeStreamFrame" to serialize and encrypt the packet. However,  CreateAndSerializeStreamFrame can return with the "AppendPacketHead failed" error. When this error happens, the code is expected to switch back to execute its slow path "packet_generator_.ConsumeData".  But the current code does not correctly follow this design. Should we change the code to prevent any regression here? 

Did this work before? Yes 

Does this work in other browsers? Yes

Chrome version: 55.0.2883.95  Channel: stable
OS Version: OS X 10.12.2
Flash Version: Shockwave Flash 24.0 r0