Fix HTTP client eviction timer bug
Fix HTTP client eviction timer bug

The HTTP client eviction timer should only be cancled and nulled out
when there are no client connections at all.

R=whesse@google.com

BUG=
TEST=

Review URL: https://chromiumcodereview.appspot.com//10693091

git-svn-id: c93d8a2297af3b929165606efe145742a534bc71@9404 260f80e4-7a28-3924-810f-c04153c831b5

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk