Bug 212505 Use default script ID to skip script debugging
In Dte side, when compile or evaluate java script, it would pass in a script source id. This kind of id is currenlty used by report script debugger. So to skip redundant processing for such kind of internal script evaluating, dte need pass in a default ID, which is defined as ScriptExpression.defaultID. If this id is already used for particular meaning and it can not pass in the default ID, we need define them as public constants and let script debugger check and skip them as well.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/executor/ExecutionContext.java
/**
	 * @return Returns the action handler.
	 */
	public IHTMLImageHandler getImageHandler( )
	{
		return renderOption.getImageHandler( );
	}
	
	/**
	 * return application class loader.
	 * The application class loader is used to load the report item event handle and 
	 * java classes called in the javascript.
	 * @return class loader
	 */
	public ClassLoader getApplicationClassLoader( )
	{
		return applicationClassLoader;
	}
	/**
	 * the application class loader.
	 * 
	 * The class loader first try to the load the class as following sequence:
	 * <li>1. standard java class loader,
	 * <li>2. classloader setted through the appContext.
	 * <li>3. CLASSPATH setted by WEBAPP_CLASSPATH_KEY
	 * <li>4. PROJECT_CLASSPATH_KEY
	 * <li>5. WORKSAPCE_CLASSPATH_KEY
	 * <li>6. JARs define in the report design
	 */
	static private class ApplicationClassLoader extends ClassLoader