Bug 81983 [preferences] Disabling and enabling folding on small file takes forever
3.1 M4 Using enable/disable folding on a small CU takes forever. This is caused by the recent change to apply the preference to all Java editors. In another (hidden) window (Debug) I had StyledText open which (understandably) took long to react on the preference change. Non-visible editor's should not react to this change until they become visible.
org.eclipse.jdt.ui/ui/org/eclipse/jdt/internal/ui/javaeditor/JavaEditor.java
* {@inheritDoc}
		 */
		public String getDefaultString(String name) {
			return STRING_DEFAULT_DEFAULT;
		}
		/**
		 * {@inheritDoc}
		 */
		public double getDouble(String name) {
			double value= DOUBLE_DEFAULT_DEFAULT;
			String s= (String) fOptions.get(name);
			if (s != null) {
				try {
					value= new Double(s).doubleValue();
				} catch (NumberFormatException e) {
				}
			}
			return value;
		}
		/**
		 * {@inheritDoc}
		 */
		public float getFloat(String name) {
			float value= FLOAT_DEFAULT_DEFAULT;
			String s= (String) fOptions.get(name);
			if (s != null) {
				try {
					value= new Float(s).floatValue();
				} catch (NumberFormatException e) {
				}