Fix trailing whitespace in .cpp, .h, and .idl files

Source/core/dom/MouseEvent.cpp

Index: Source/core/dom/MouseEvent.cpp
diff --git a/Source/core/dom/MouseEvent.cpp b/Source/core/dom/MouseEvent.cpp
index e11d1d85bae1ca5cfb61a95c02f29761b1b9b914..2d5f32822f03fb1a0fbcbd945c25684243572758 100644
--- a/Source/core/dom/MouseEvent.cpp
+++ b/Source/core/dom/MouseEvent.cpp
@@ -181,7 +181,7 @@ bool MouseEvent::isDragEvent() const
 int MouseEvent::which() const
 {
     // For the DOM, the return values for left, middle and right mouse buttons are 0, 1, 2, respectively.
-    // For the Netscape "which" property, the return values for left, middle and right mouse buttons are 1, 2, 3, respectively. 
+    // For the Netscape "which" property, the return values for left, middle and right mouse buttons are 1, 2, 3, respectively.
     // So we must add 1.
     if (!m_buttonDown)
         return 0;