Add Cronet experimental option for host cache persistence

components/cronet/android/test/javatests/src/org/chromium/net/ExperimentalOptionsTest.java

Index: components/cronet/android/test/javatests/src/org/chromium/net/ExperimentalOptionsTest.java
diff --git a/components/cronet/android/test/javatests/src/org/chromium/net/ExperimentalOptionsTest.java b/components/cronet/android/test/javatests/src/org/chromium/net/ExperimentalOptionsTest.java
index 3509479f037f6b6be34c0312bedf5e5ae91507d6..a975239dfdb1b9e05a9eef143d5a4090ad7bd1f5 100644
--- a/components/cronet/android/test/javatests/src/org/chromium/net/ExperimentalOptionsTest.java
+++ b/components/cronet/android/test/javatests/src/org/chromium/net/ExperimentalOptionsTest.java
@@ -10,7 +10,9 @@ import org.json.JSONObject;
 
 import org.chromium.base.Log;
 import org.chromium.base.PathUtils;
+import org.chromium.base.annotations.JNINamespace;
 import org.chromium.base.test.util.Feature;
+import org.chromium.net.impl.CronetUrlRequestContext;
 
 import java.io.File;
 import java.io.FileInputStream;
@@ -20,6 +22,7 @@ import java.io.IOException;
 /**
  * Tests for experimental options.
  */
+@JNINamespace("cronet")
 public class ExperimentalOptionsTest extends CronetTestBase {
     private static final String TAG = ExperimentalOptionsTest.class.getSimpleName();
     private ExperimentalCronetEngine.Builder mBuilder;
@@ -135,4 +138,38 @@ public class ExperimentalOptionsTest extends CronetTestBase {
         }
         return false;
     }
+
+    @MediumTest
+    @Feature({"Cronet"})
+    @OnlyRunNativeCronet
+    // Tests that basic Cronet functionality works when host cache persistence is enabled, and that
+    // persistence works.
+    public void testHostCachePersistence() throws Exception {
+        mBuilder.setStoragePath(getTestStorage(getContext()));
+
+        // Set a short delay so the pref gets written quickly.
+        JSONObject staleDns = new JSONObject()
+                                      .put("enable", true)
+                                      .put("allow_other_network", true)
+                                      .put("persist_to_disk", true)
+                                      .put("persist_timer_ms", 0);
+        JSONObject experimentalOptions = new JSONObject().put("StaleDNS", staleDns);
+        mBuilder.setExperimentalOptions(experimentalOptions.toString());
+        CronetUrlRequestContext context = (CronetUrlRequestContext) mBuilder.build();
+
+        // Normal test requests won't interact with the HostCache, so access it directly from native
+        // code instead, then wait for the write to prefs.
+        nativeWriteToHostCache(context.getUrlRequestContextAdapter());
+        Thread.sleep(100);
+
+        // Shut down before reading prefs file to make sure prefs are flushed to disk.
+        context.shutdown();
+
+        File file = new File(getTestStorage(getContext()) + "/prefs/local_prefs.json");
+        assertFileContainsString(file, "host_cache");
+        assertFileContainsString(file, "host-cache-test-host");
+    }
+
+    // Sets a host cache entry with hostname "host-cache-test-host".
+    private static native void nativeWriteToHostCache(long adapter);
 }