Make JsEngine::Evaluate() return a wrapper for v8::Value to accessdifferent variable types easily

test/JsEngine.cpp

Index: test/JsEngine.cpp
===================================================================
--- a/test/JsEngine.cpp
+++ b/test/JsEngine.cpp
@@ -45,28 +45,30 @@ public:
 
 TEST(JsEngineTest, EvaluateAndCall)
 {
   ThrowingFileReader fileReader;
   ThrowingErrorCallback errorCallback;
   AdblockPlus::JsEngine jsEngine(&fileReader, 0, &errorCallback);
   const std::string source = "function hello() { return 'Hello'; }";
   jsEngine.Evaluate(source);
-  const std::string result = jsEngine.Evaluate("hello()");
-  ASSERT_EQ("Hello", result);
+  AdblockPlus::JsValuePtr result = jsEngine.Evaluate("hello()");
+  ASSERT_EQ(true, result->IsString());
+  ASSERT_EQ("Hello", result->AsString());
 }
 
 TEST(JsEngineTest, LoadAndCall)
 {
   StubFileReader fileReader;
   ThrowingErrorCallback errorCallback;
   AdblockPlus::JsEngine jsEngine(&fileReader, 0, &errorCallback);
   jsEngine.Load("hello.js");
-  const std::string result = jsEngine.Evaluate("hello()");
-  ASSERT_EQ("Hello", result);
+  AdblockPlus::JsValuePtr result = jsEngine.Evaluate("hello()");
+  ASSERT_EQ(true, result->IsString());
+  ASSERT_EQ("Hello", result->AsString());
 }
 
 TEST(JsEngineTest, LoadBadStreamFails)
 {
   BadFileReader fileReader;
   ThrowingErrorCallback errorCallback;
   AdblockPlus::JsEngine jsEngine(&fileReader, 0, &errorCallback);
   ASSERT_ANY_THROW(jsEngine.Load("hello.js"));