find/replace overlay: clean up PreferenceChangeListener

The PreferenceChangeListener now starts listening when an Overlay was
created and stops listening once the Overlay is disposed of. Fixes a
previous resource leak.

fixes jdt#1444

bundles/org.eclipse.ui.workbench.texteditor/src/org/eclipse/ui/texteditor/FindReplaceAction.java

@@ -302,8 +302,6 @@ public FindReplaceAction(ResourceBundle bundle, String prefix, IWorkbenchPart wo
 		Assert.isLegal(workbenchPart != null);
 		fWorkbenchPart= workbenchPart;
 		update();
-
-		hookDialogPreferenceListener();
 	}
 
 	/**
@@ -331,8 +329,6 @@ public FindReplaceAction(ResourceBundle bundle, String prefix, Shell shell, IFin
 		fTarget= target;
 		fShell= shell;
 		update();
-
-		hookDialogPreferenceListener();
 	}
 
 	/**
@@ -354,15 +350,18 @@ public FindReplaceAction(ResourceBundle bundle, String prefix, IWorkbenchWindow
 		super(bundle, prefix);
 		fWorkbenchWindow= workbenchWindow;
 		update();
-
-		hookDialogPreferenceListener();
 	}
 
 	private void hookDialogPreferenceListener() {
 		IEclipsePreferences preferences = InstanceScope.INSTANCE.getNode(INSTANCE_SCOPE_NODE_NAME);
 		preferences.addPreferenceChangeListener(overlayDialogPreferenceListener);
 	}
 
+	private void removeDialogPreferenceListener() {
+		IEclipsePreferences preferences = InstanceScope.INSTANCE.getNode(INSTANCE_SCOPE_NODE_NAME);
+		preferences.removePreferenceChangeListener(overlayDialogPreferenceListener);
+	}
+
 	@Override
 	public void run() {
 		if (fTarget == null) {
@@ -420,12 +419,14 @@ private void showOverlayInEditor() {
 				shellToUse = fShell;
 			}
 			overlay = new FindReplaceOverlay(shellToUse, fWorkbenchPart, fTarget);
+			hookDialogPreferenceListener();
 
 			FindReplaceOverlayFirstTimePopup.displayPopupIfNotAlreadyShown(shellToUse);
 		}
 
 		overlay.setPositionToTop(shouldPositionOverlayOnTop());
 		overlay.open();
+		overlay.getShell().addDisposeListener(__ -> removeDialogPreferenceListener());
 	}
 
 	@Override