Fix bug where WebPage.evaluate had a syntax error.

It now creates a proper anonymous function (which passes this for global context)

python/webpage.py

@@ -269,7 +269,7 @@ class WebPage(QObject):
 
     @pyqtSlot(str, result='QVariant')
     def evaluate(self, code):
-        function = '(%s)()' % code
+        function = '(function(){%s}).call(this);' % code
         return self.m_mainFrame.evaluateJavaScript(function)
 
     @pyqtSlot(str, str, 'QVariantMap')

src/webpage.cpp

@@ -209,7 +209,7 @@ QVariantMap WebPage::paperSize() const
 
 QVariant WebPage::evaluate(const QString &code)
 {
-    QString function = "(" + code + ")()";
+    QString function = "(function(){" + code + "}).call(this);";
     return m_mainFrame->evaluateJavaScript(function);
 }