Problem during restore of ClassFileEditor

eclipse-jdt/eclipse.jdt.ui#2347

- Changed the RequiredPluginsClasspathContainer interface from
IClasspathContainer to IAsyncClasspathContainer

Author: mehmet-karaman

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/RequiredPluginsClasspathContainer.java

@@ -42,8 +42,8 @@
 import org.eclipse.core.runtime.IExtensionRegistry;
 import org.eclipse.core.runtime.IPath;
 import org.eclipse.core.runtime.Platform;
+import org.eclipse.jdt.core.IAsyncClasspathContainer;
 import org.eclipse.jdt.core.IClasspathAttribute;
-import org.eclipse.jdt.core.IClasspathContainer;
 import org.eclipse.jdt.core.IClasspathEntry;
 import org.eclipse.jdt.core.JavaCore;
 import org.eclipse.osgi.service.resolver.BaseDescription;
@@ -70,7 +70,8 @@
 import aQute.bnd.build.Workspace;
 import aQute.bnd.osgi.Constants;
 
-public class RequiredPluginsClasspathContainer extends PDEClasspathContainer implements IClasspathContainer {
+public class RequiredPluginsClasspathContainer extends PDEClasspathContainer
+		implements IAsyncClasspathContainer {
 
 	@SuppressWarnings("nls")
 	private static final Set<String> JUNIT5_RUNTIME_PLUGINS = Set.of("org.junit", //
@@ -736,4 +737,14 @@ public List<IProject> getAllProjectDependencies() {
 			addImportedPackages = false;
 		}
 	}
+
+	@Override
+	public boolean isInitialized() {
+		return fEntries != null;
+	}
+
+	@Override
+	public void initialize() {
+		getClasspathEntries();
+	}
 }