[Extensions Bindings] Add chrome.runtime.lastError support

extensions/renderer/api_binding_test_util.h

 // 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.
 
 #ifndef EXTENSIONS_RENDERER_API_BINDING_TEST_UTIL_H_
 #define EXTENSIONS_RENDERER_API_BINDING_TEST_UTIL_H_
 
 #include <memory>
 #include <string>
 
@@ skipping 19 matching lines @@
 std::unique_ptr<base::ListValue> ListValueFromString(base::StringPiece str);
 
 // As above, but returning a DictionaryValue.
 std::unique_ptr<base::DictionaryValue> DictionaryValueFromString(
     base::StringPiece str);
 
 // Converts the given |value| to a JSON string. EXPECTs the conversion to
 // succeed.
 std::string ValueToString(const base::Value& value);
 
+// Converts the given |value| to a string. Returns "empty", "undefined", "null",
+// or "function" for unserializable values. Note this differs from
+// gin::V8ToString, which only accepts v8::String values.
+std::string V8ToString(v8::Local<v8::Value> value,
+                       v8::Local<v8::Context> context);
+
 // Returns a v8::Value result from compiling and running |source|, or an empty
 // local on failure.
 v8::Local<v8::Value> V8ValueFromScriptSource(v8::Local<v8::Context> context,
                                              base::StringPiece source);
 
 // Returns a v8::Function parsed from the given |source|. EXPECTs the conversion
 // to succeed.
 v8::Local<v8::Function> FunctionFromString(v8::Local<v8::Context> context,
                                            base::StringPiece source);
 
@@ skipping 65 matching lines @@
 
 // As above, but returns a JSON-serialized version of the value, or
 // "undefined", "null", "function", or "empty".
 std::string GetStringPropertyFromObject(v8::Local<v8::Object> object,
                                         v8::Local<v8::Context> context,
                                         base::StringPiece key);
 
 }  // extensions
 
 #endif  // EXTENSIONS_RENDERER_API_BINDING_TEST_UTIL_H_