Add testHttpEngine_EnableHttpCache

New test for enable caching API. CtsTestServer doesn't add a
`cache-control: max-age=X` header, this stops Cronet HttpEngine from
caching the response. Use a non-hermetic server to circumvent that.

Test: m & test run
Change-Id: I6852c72590146892a3175ce8c23668e3abda0dbd
diff --git a/Cronet/tests/cts/src/android/net/http/cts/HttpEngineTest.java b/Cronet/tests/cts/src/android/net/http/cts/HttpEngineTest.java
index 8663a67..689bfeb 100644
--- a/Cronet/tests/cts/src/android/net/http/cts/HttpEngineTest.java
+++ b/Cronet/tests/cts/src/android/net/http/cts/HttpEngineTest.java
@@ -23,6 +23,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsString;
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
 
 import android.content.Context;
@@ -90,6 +91,41 @@
     }
 
     @Test
+    public void testHttpEngine_EnableHttpCache() {
+        // We need a server which sets cache-control != no-cache.
+        String url = "https://www.example.com";
+        mEngine =
+                mEngineBuilder
+                        .setStoragePath(
+                                InstrumentationRegistry.getInstrumentation()
+                                        .getContext()
+                                        .getApplicationInfo()
+                                        .dataDir)
+                        .setEnableHttpCache(HttpEngine.Builder.HTTP_CACHE_DISK, 100 * 1024)
+                        .build();
+
+        UrlRequest.Builder builder =
+                mEngine.newUrlRequestBuilder(url, mCallback, mCallback.getExecutor());
+        mRequest = builder.build();
+        mRequest.start();
+        // This tests uses a non-hermetic server. Instead of asserting, assume the next callback.
+        // This way, if the request were to fail, the test would just be skipped instead of failing.
+        mCallback.assumeCallback(ResponseStep.ON_SUCCEEDED);
+        UrlResponseInfo info = mCallback.mResponseInfo;
+        assumeOKStatusCode(info);
+        assertFalse(info.wasCached());
+
+        mCallback = new TestUrlRequestCallback();
+        builder = mEngine.newUrlRequestBuilder(url, mCallback, mCallback.getExecutor());
+        mRequest = builder.build();
+        mRequest.start();
+        mCallback.assumeCallback(ResponseStep.ON_SUCCEEDED);
+        info = mCallback.mResponseInfo;
+        assertOKStatusCode(info);
+        assertTrue(info.wasCached());
+    }
+
+    @Test
     public void testHttpEngine_DisableHttp2() throws Exception {
         mEngine = mEngineBuilder.setEnableHttp2(false).build();
         UrlRequest.Builder builder =
diff --git a/Cronet/tests/cts/src/android/net/http/cts/UrlRequestTest.java b/Cronet/tests/cts/src/android/net/http/cts/UrlRequestTest.java
index 5256bae..3665123 100644
--- a/Cronet/tests/cts/src/android/net/http/cts/UrlRequestTest.java
+++ b/Cronet/tests/cts/src/android/net/http/cts/UrlRequestTest.java
@@ -113,8 +113,9 @@
         String testData = "test";
         UrlRequest.Builder builder = createUrlRequestBuilder(mTestServer.getEchoBodyUrl());
 
-        TestUploadDataProvider dataProvider = new TestUploadDataProvider(
-                TestUploadDataProvider.SuccessCallbackMode.SYNC, mCallback.getExecutor());
+        TestUploadDataProvider dataProvider =
+                new TestUploadDataProvider(
+                        TestUploadDataProvider.SuccessCallbackMode.SYNC, mCallback.getExecutor());
         dataProvider.addRead(testData.getBytes());
         builder.setUploadDataProvider(dataProvider, mCallback.getExecutor());
         builder.addHeader("Content-Type", "text/html");