feat(3p/absl): import StatusOr from tensorflow

Additionally, add tests for the macros. A future CL will enable the tests in CI.

Change-Id: Id4445a1aa65bf6751b87606f37654f3fc6d20efc
Tested-By: kanepyork <rikingcoding@gmail.com>
Reviewed-on: https://cl.tvl.fyi/c/depot/+/1274
Reviewed-by: tazjin <mail@tazj.in>
Reviewed-by: glittershark <grfn@gws.fyi>
Tested-by: BuildkiteCI

third_party/abseil_cpp/absl/status/statusor.cc

@@ -0,0 +1,48 @@
+/* Copyright 2017 The TensorFlow 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 "absl/status/statusor.h"
+
+#include "absl/base/internal/raw_logging.h"
+
+namespace absl {
+ABSL_NAMESPACE_BEGIN
+
+namespace internal_statusor {
+
+#define ABSL_STATUSOR_INTERNAL_BAD_OK_MSG "An OK status is not a valid " \
+  "constructor argument to StatusOr<T>"
+
+void Helper::HandleInvalidStatusCtorArg(Status* status) {
+  ABSL_RAW_LOG(ERROR, ABSL_STATUSOR_INTERNAL_BAD_OK_MSG);
+  // Fall back to kInternal.
+  *status = InternalError(ABSL_STATUSOR_INTERNAL_BAD_OK_MSG);
+}
+
+#undef ABSL_STATUSOR_INTERNAL_BAD_OK_MSG
+
+void Helper::Crash(const Status& status) {
+#ifdef ABSL_HAVE_EXCEPTIONS
+  throw status;
+#else
+  std::string status_debug = status.ToString();
+  ABSL_RAW_LOG(FATAL, "Attempting to fetch value instead of handling error: %s", status_debug.c_str());
+  abort();   // TODO(calabrese) Remove once RAW_LOG FATAL is noreturn.
+#endif
+}
+}  // namespace internal_statusor
+
+ABSL_NAMESPACE_END
+}  // namespace absl