Disable flaky test NetworkContextTest.CloseIdleConnections.

TBR=cmumford@chromium.org,jam@chromium.org

Bug: 905423
Change-Id: I2572c956ac4ef4fcc0553cd595fb93679b79ca12
Reviewed-on: https://chromium-review.googlesource.com/c/1345513Reviewed-by: Anders Ruud <andruud@chromium.org>
Commit-Queue: Anders Ruud <andruud@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609966}

services/network/network_context_unittest.cc

@@ -3598,7 +3598,8 @@ TEST_F(NetworkContextTest, CloseAllConnections) {
   EXPECT_EQ(num_sockets, 0);
 }
 
-TEST_F(NetworkContextTest, CloseIdleConnections) {
+// Flaky; see http://crbug.com/905423
+TEST_F(NetworkContextTest, DISABLED_CloseIdleConnections) {
   std::unique_ptr<NetworkContext> network_context =
       CreateContextWithParams(CreateContextParams());