Bug 199834 Enable access to IContent object in IReportItemPresentation layer
In IReportItemPresentation layer, the extended item may want to access properties from current IContent object, for example, bookmark, content style. So we need expose the content object in this layer.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/extension/IReportItemPresentation.java
* @return the returned value could be different depending on the type of
	 *         the output. For image, returns an input stream or byte array that
	 *         the engine could retrieve data from
	 * @throws BirtException
	 *             throws exception when there is a problem processing the
	 *             extended item
	 */
	public abstract Object onRowSets( IRowSet[] rowSets ) throws BirtException;
	/**
	 * Get the size of the extended item. The size is a Dimension object. The
	 * width and height can only be in absolute units (inch, mm, etc.) or pixel.
	 * It can not be a relative size such as 150% or 1.2em. Notice that an
	 * extended item can obtain its design-time size information by querying DE.
	 * This function is needed because the actual size may not be the same as
	 * the design-time size.
	 * 
	 * @return the size of the extended item. Return null if the size does not
	 *         matter or can not be determined.
	 */
	public Size getSize( );
	/**
	 * Performs clean up work
	 */
	public void finish( );
	/**
	 * Set dynamic style.
	 */
	public void setDynamicStyle( IStyle style );
}