VintfObject::verify() will fetch data from device

- If no info is provided then all data is fetched from device.
- Add hook to mock retrieving files from device.
- Add test.
- Print more detailed messages on AVB failures.

Test: Ran vintf_object_test and libvintf_test
Bug: 37863689
Bug: 36814984
Change-Id: Ia33f4e2e73c863bc0f8f68f5ed61c30df8eff53d
Merged-In: Ia33f4e2e73c863bc0f8f68f5ed61c30df8eff53d
diff --git a/utils.cpp b/utils.cpp
new file mode 100644
index 0000000..3c4d2e7
--- /dev/null
+++ b/utils.cpp
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "utils.h"
+
+namespace android {
+namespace vintf {
+namespace details {
+
+FileFetcher fetcher;
+FileFetcher* gFetcher = &fetcher;
+
+}  // namespace details
+}  // namespace vintf
+}  // namespace android