if a tooltip, do as tooltip do

The fake tooltip duplication is not nice.

src/plugins/cpptools/cppcodecompletion.cpp

@@ -300,7 +300,8 @@ FunctionArgumentWidget::FunctionArgumentWidget():
     connect(downArrow, SIGNAL(clicked()), SLOT(nextPage()));
 
     setTextFormat(Qt::RichText);
-    setMargin(1);
+    setMargin(1 + style()->pixelMetric(QStyle::PM_ToolTipLabelFrameWidth, 0, this));
+    setIndent(1);
 
     qApp->installEventFilter(this);
 }