Create CrashReportDatabase interface, a test, and a Mac implementation.

client/crash_report_database.cc

+// Copyright 2015 The Crashpad Authors. All rights reserved.
+//
+// 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 "client/crash_report_database.h"
+
+namespace crashpad {
+
+CrashReportDatabase::Report::Report()
+    : uuid(), file_path(), id(), creation_time(0), uploaded(false),
+      last_upload_attempt_time(0), upload_attempts(0) {
+}
+
+}  // namespace crashpad