headless: Add error reporter utility

headless/public/util/error_reporter.cc

Index: headless/public/util/error_reporter.cc
diff --git a/headless/public/util/error_reporter.cc b/headless/public/util/error_reporter.cc
new file mode 100644
index 0000000000000000000000000000000000000000..54c0758b71ddd940e3ff76aee3cdc62cefea3203
--- /dev/null
+++ b/headless/public/util/error_reporter.cc
@@ -0,0 +1,51 @@
+// 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(base::StringPiece description) {
+  std::stringstream error;
+  for (size_t i = 0; i < path_.size(); i++) {
+    if (!path_[i]) {
+      DCHECK_EQ(i + 1, path_.size());
+      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