Keep push streams open until they are claimed.  The previous change I did changed this (so that streams are closed when they get EOF, even though the unclaimed stream is active), but it breaks the invariants for spdy_http_stream and checking when a stream is closed.  Both models have advantages, going back to the original mechanism.
Keep push streams open until they are claimed.  The previous change I did
changed this (so that streams are closed when they get EOF, even though
the unclaimed stream is active), but it breaks the invariants for
spdy_http_stream and checking when a stream is closed.  Both models have
advantages, going back to the original mechanism.

BUG=none
TEST=Working on the unittest

Review URL: http://codereview.chromium.org/3198012

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@57398 0039d316-1c4b-4281-b951-d872f2087c98

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