Constructs a ColorSplitBehavior for combining a color button and a menu.
To use this, provide a goog.ui.ColorButton which will be attached with
a goog.ui.ColorMenuButton (with no caption).
Whenever a color is selected from the ColorMenuButton, it will be placed in
the ColorButton and the user can apply it over and over (by clicking the
ColorButton).
Primary use case - setting the color of text/background in a text editor.