Revert 129277 - Revert 127893 - Attempting to re-land the feature.

Revert 129277 - Revert 127893 - Attempting to re-land the feature.

Revert 127730 - Revert 127717 - Revert 118788 - Revert 113405 - Revert 113305 - Revert 113300 - Revert 112134 - Revert 112130 - Close idle connections / SPDY sessions when needed

Due to the idle connection state being held by different socket pools, it's possible for one socket pool to hold an idle socket in a lower layer socket pool. From the lower level socket pool's perspective, the socket is being "actively" used. From the higher socket pool's (including SpdySession, which is more of a connection manager) perspective, the connection is idle and can be closed if we have hit a limit.

Normally this isn't a big deal, except when we have a lot of idle SPDY connections and are connecting via a proxy, so we have low connection limits through the proxy server. We address this problem by allowing lower-level socket pools to tell higher level socket pools to close a socket.

Fixed ASAN test failures by removing .Times(1) and .Times(2) from CloseMultipleIdleSocketsHeldByLayeredPoolWhenNeeded unittest (this removes the tests relying on the order of std::set in CloseOneIdleConnectionInLayeredPool). ASAN is prob
ably causing the memory allocator to allocate the pools differently. The std::set is ordered by LayeredPool* which is the address of the LayeredPool (willchan).

Added NET_EXPORT for layered_pool class defintion to fix windows shared compile.

BUG=62364, 92244, 109876, 110368
TEST=

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=127717

Review URL: https://chromiumcodereview.appspot.com/9667016

TBR=rch@chromium.org

TBR=dharani@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=129293