headless: Add error reporter utility

headless/public/util/error_reporter.cc

+// Copyright 2016 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 "headless/public/util/error_reporter.h"
+
+#include <sstream>
+
+#include "base/logging.h"
+
+namespace headless {
+
+ErrorReporter::ErrorReporter() {}
+
+ErrorReporter::~ErrorReporter() {}
+
+void ErrorReporter::Push() {
+  path_.push_back(nullptr);
+}
+
+void ErrorReporter::Pop() {
+  path_.pop_back();
+}
+
+void ErrorReporter::SetName(const char* name) {
+  DCHECK(!path_.empty());
+  path_[path_.size() - 1] = name;
+}
+
+void ErrorReporter::AddError(const char* description) {
+  std::stringstream error;
+  for (size_t i = 0; i < path_.size(); i++) {
+    if (!path_[i])

[altimin, 2016/04/11 15:30:05]

I wonder if ignoring the rest of the path_ is a good idea to do when nullptr is
encountered (especially when we have to call SetName manually).

DCHECK maybe?

[Sami, 2016/04/11 15:37:15]

Good idea, added.

+      break;
+    if (i)
+      error << '.';
+    error << path_[i];
+  }
+  if (error.tellp())
+    error << ": ";
+  error << description;
+  errors_.push_back(error.str());
+}
+
+bool ErrorReporter::HasErrors() const {
+  return !errors_.empty();
+}
+
+}  // namespace headless