Add the JNI code in order to let Java use the InterestsFetcher.

chrome/browser/android/interests_service_unittest.cc

Index: chrome/browser/android/interests_service_unittest.cc
diff --git a/chrome/browser/android/interests_service_unittest.cc b/chrome/browser/android/interests_service_unittest.cc
new file mode 100644
index 0000000000000000000000000000000000000000..e006d92f4fe9d14c0a67cc0d12d24259d3a89bfa
--- /dev/null
+++ b/chrome/browser/android/interests_service_unittest.cc
@@ -0,0 +1,46 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <jni.h>
+
+#include "base/android/jni_android.h"
+#include "chrome/browser/android/interests_service.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+using base::android::AttachCurrentThread;
+
+namespace {
+std::vector<InterestsFetcher::Interest> GetEmptyResponse() {
+  return std::vector<InterestsFetcher::Interest>();
+}
+
+std::vector<InterestsFetcher::Interest> GetSuccessfulResponse() {
+  std::vector<InterestsFetcher::Interest> res;
+  res.push_back(
+      InterestsFetcher::Interest{"Google", "https://fake.com/fake.png", 0.9});
+  res.push_back(InterestsFetcher::Interest{"Google Chrome",
+                                           "https://fake.com/fake.png", 0.98});
+  return res;
+}
+
+}  // namespace
+
+class InterestsServiceTest : public testing::Test {
+ public:
+  InterestsServiceTest() {}
+};
+
+TEST_F(InterestsServiceTest, ConvertEmptyResponse) {
+  JNIEnv* env = AttachCurrentThread();
+  jobjectArray j_interests =
+      InterestsService::ConvertInterestsToJava(GetEmptyResponse());
+  CHECK_EQ(env->GetArrayLength(j_interests), 0);

[Marc Treib, 2015/09/11 16:02:14]

EXPECT_EQ (CHECK will make the test crash)

Also, the expected value goes first (the error message on failure is something
like "should be param_1 but is param_2").

[tache, 2015/09/18 09:41:21]

Done.

+}
+
+TEST_F(InterestsServiceTest, ConvertSucccesfulResponse) {
+  JNIEnv* env = AttachCurrentThread();
+  jobjectArray j_interests =
+      InterestsService::ConvertInterestsToJava(GetSuccessfulResponse());
+  CHECK_EQ(env->GetArrayLength(j_interests), 2);
+}