[Extensions Bindings] Add chrome.runtime.lastError support

extensions/renderer/api_last_error.h

+// Copyright 2017 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.
+
+#ifndef EXTENSIONS_RENDERER_API_LAST_ERROR_H_
+#define EXTENSIONS_RENDERER_API_LAST_ERROR_H_
+
+#include <string>
+
+#include "base/callback.h"
+#include "base/macros.h"
+#include "v8/include/v8.h"
+
+namespace extensions {
+
+// Handles creating and clearing a 'lastError' property to hold the last error
+// set by an extension API function.
+class APILastError {
+ public:
+  // Returns the object the 'lastError' property should be exposed on for the
+  // given context.
+  using GetParent =
+      base::Callback<v8::Local<v8::Object>(v8::Local<v8::Context>)>;
+
+  APILastError(const GetParent& get_parent);

[jbroman, 2017/02/13 19:41:27]

explicit

[Devlin, 2017/02/14 04:57:08]

Done.

+  APILastError(APILastError&& other);

[jbroman, 2017/02/13 19:41:27]

It's a little weird to have a move constructor without a move assignment
operator, but I guess you never need to move-assign at present?

[Devlin, 2017/02/14 04:57:08]

Right.  Not sure if we have a preferred style here, so I default to "if it isn't
needed, don't add it."

+  ~APILastError();
+
+  // Sets the last error for the given |context| to |error|.
+  void SetError(v8::Local<v8::Context> context, const std::string& error);
+
+  // Clears the last error in the given |context|. If |report_if_unchecked| is
+  // true and the developer didn't check the error, this throws an exception.
+  void ClearError(v8::Local<v8::Context> context, bool report_if_unchecked);
+
+ private:
+  GetParent get_parent_;
+
+  DISALLOW_COPY_AND_ASSIGN(APILastError);
+};
+
+}  // namespace extensions
+
+#endif  // EXTENSIONS_RENDERER_API_LAST_ERROR_H_