Disable DevToolsNetworkOfflineEmulationTest.RunAsyncTest

The test is flaky.

TBR=fdegans@chromium.org

Bug: 1037652
Change-Id: I71dfab70de4baacf214ddf0f7375bf15c3ffac3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1981112Reviewed-by: Fabrice de Gans-Riberi <fdegans@chromium.org>
Commit-Queue: Fabrice de Gans-Riberi <fdegans@chromium.org>
Cr-Commit-Position: refs/heads/master@{#727268}

headless/lib/headless_devtools_client_browsertest.cc

@@ -668,7 +668,8 @@ class DevToolsNetworkOfflineEmulationTest
   }
 };
 
-HEADLESS_ASYNC_DEVTOOLED_TEST_F(DevToolsNetworkOfflineEmulationTest);
+// Flaky. https://crbug.com/1037652
+DISABLED_HEADLESS_ASYNC_DEVTOOLED_TEST_F(DevToolsNetworkOfflineEmulationTest);
 
 class RawDevtoolsProtocolTest
     : public HeadlessAsyncDevTooledBrowserTest,