Docs added.

openapi/src/com/intellij/ExtensionPoints.java

@@ -0,0 +1,35 @@
+package com.intellij;
+
+/**
+ * Extension points provided by IDEA core are listed here.
+ */
+public interface ExtensionPoints {
+  /**
+   * This extension point should be used instead of former application-components, project-components, module-components.
+   * Extension declaration sample is as follows:
+   * <pre>
+   * &lt;extensions xmlns="com.intellij"&gt;
+   *   &lt;component area="IDEA_PROJECT"&gt;
+   *     &lt;implementation&gt;my.plugin.pagckage.MyProjectComponent&lt;/implementation&gt;
+   *   &lt;/component&gt;
+   * &lt;/extensions&gt;
+   * </pre>
+   *
+   * Possible registration areas are IDEA_PROJECT, MODULE_PROJECT which stand for ProjectComponent and ModuleComponent correspondingly.
+   * If area attribute is ommited the component will be registered in root area which corresponds to ApplicationComponent.
+   */
+  String COMPONENT = "com.intellij.component";
+
+  /**
+   * This extension point allows a plugin vendor to provide the user ability to report fatal errors (aka exceptions) that happened in
+   * their plugin code.
+   * Extension declaration sample is as follows:
+   * <pre>
+   * &lt;extensions xmlns="com.intellij"&gt;
+   *   &lt;errorHandler implementation="my.plugin.package.MyErrorHandler"/&gt;
+   * &lt;/extensions&gt;
+   * </pre>
+   * my.plugin.package.MyErrorHandler class must implement {@link com.intellij.openapi.diagnostic.ErrorReportSubmitter} abstract class.
+   */
+  String ERROR_HANDLER = "com.intellij.errorHandler";
+}

openapi/src/com/intellij/openapi/diagnostic/ErrorReportSubmitter.java

@@ -6,24 +6,40 @@ import com.intellij.openapi.extensions.PluginDescriptor;
 import java.awt.*;
 
 /**
- * Created by IntelliJ IDEA.
- * User: max
- * Date: Feb 17, 2005
- * Time: 9:11:44 PM
- * To change this template use File | Settings | File Templates.
+ * This class should be extended by plugin vendor and provided by means of {@link com.intellij.ExtensionPoints#ERROR_HANDLER} if
+ * reporting errors that happened in plugin code to vendor is desirable.
  */
 public abstract class ErrorReportSubmitter implements PluginAware {
-  public final static String ERROR_HANDLER_EXTENSION_POINT = "com.intellij.errorHandler";
   private PluginDescriptor myPlugin;
 
+  /**
+   * Called by the framework. Allows to identify the plugin that provided this extension.
+   * @param plugin
+   */
   public void setPluginDescriptor(PluginDescriptor plugin) {
     myPlugin = plugin;
   }
 
+  /**
+   * @return plugin that provided this particular extension
+   */
   public PluginDescriptor getPluginDescriptor() {
     return myPlugin;
   }
 
+  /**
+   * @return "Report to vendor" action text to be used in Error Reporter user interface. For example: "Report to JetBrains".
+   */
   public abstract String getReportActionText();
+
+  /**
+   * This method is called whenever fatal error (aka exception) in plugin code had happened and user decided to report this problem to
+   * plugin vendor.
+   * @param events sequence of the fatal error descriptors. Fatal errors that happened immediately one after another most probably caused
+   * by first one that happened so it's a common practice to submit only first one. Array passed is guaranteed to have at least one element.
+   * @param parentComponent one usually wants to show up a dialog asking user for additional details and probably authentication info.
+   * parentComponent parameter is passed so dialog that would come up would be properly aligned with its parent dialog (IDE Fatal Errors).
+   * @return submission result status.
+   */
   public abstract SubmittedReportInfo submit(IdeaLoggingEvent[] events, Component parentComponent);
 }

source/com/intellij/diagnostic/IdeErrorsDialog.java

@@ -8,6 +8,7 @@ package com.intellij.diagnostic;
  * @author kir, max
  */
 
+import com.intellij.ExtensionPoints;
 import com.intellij.ide.BrowserUtil;
 import com.intellij.ide.plugins.PluginManager;
 import com.intellij.ide.reporter.ScrData;
@@ -467,7 +468,7 @@ public class IdeErrorsDialog extends DialogWrapper implements MessagePoolListene
 
   private ErrorReportSubmitter getSubmitter(final AbstractMessage logMessage) {
     final String pluginName = findPluginName(logMessage.getThrowable());
-    final Object[] reporters = Extensions.getRootArea().getExtensionPoint(ErrorReportSubmitter.ERROR_HANDLER_EXTENSION_POINT)
+    final Object[] reporters = Extensions.getRootArea().getExtensionPoint(ExtensionPoints.ERROR_HANDLER)
         .getExtensions();
     ErrorReportSubmitter submitter = null;
     for (int i = 0; i < reporters.length; i++) {

source/com/intellij/ide/plugins/PluginManager.java

@@ -1,5 +1,6 @@
 package com.intellij.ide.plugins;
 
+import com.intellij.ExtensionPoints;
 import com.intellij.diagnostic.ITNReporter;
 import com.intellij.ide.plugins.cl.IdeaClassLoader;
 import com.intellij.ide.plugins.cl.PluginClassLoader;
@@ -40,7 +41,6 @@ import java.util.zip.ZipFile;
 public class PluginManager {
   //Logger is lasy-initialized in order not to use it outside the appClassLoader
   private static Logger ourLogger = null;
-  public static final String COMPONENT_EXTENSION_POINT = "com.intellij.component";
 
   private static Logger getLogger() {
     if (ourLogger == null) {
@@ -125,12 +125,12 @@ public class PluginManager {
     Extensions.registerAreaClass("IDEA_PROJECT", null);
     Extensions.registerAreaClass("IDEA_MODULE", "IDEA_PROJECT");
 
-    Extensions.getRootArea().registerExtensionPoint(COMPONENT_EXTENSION_POINT, ComponentDescriptor.class.getName());
+    Extensions.getRootArea().registerExtensionPoint(ExtensionPoints.COMPONENT, ComponentDescriptor.class.getName());
 
     Extensions.getRootArea().getExtensionPoint(Extensions.AREA_LISTENER_EXTENSION_POINT).registerExtension(new AreaListener() {
       public void areaCreated(String areaClass, AreaInstance areaInstance) {
         if ("IDEA_PROJECT".equals(areaClass) || "IDEA_MODULE".equals(areaClass)) {
-          Extensions.getArea(areaInstance).registerExtensionPoint(COMPONENT_EXTENSION_POINT, ComponentDescriptor.class.getName());
+          Extensions.getArea(areaInstance).registerExtensionPoint(ExtensionPoints.COMPONENT, ComponentDescriptor.class.getName());
         }
       }
 
@@ -138,8 +138,8 @@ public class PluginManager {
       }
     }, LoadingOrder.FIRST);
 
-    Extensions.getRootArea().registerExtensionPoint(ErrorReportSubmitter.ERROR_HANDLER_EXTENSION_POINT, ErrorReportSubmitter.class.getName());
-    Extensions.getRootArea().getExtensionPoint(ErrorReportSubmitter.ERROR_HANDLER_EXTENSION_POINT).registerExtension(new ITNReporter());
+    Extensions.getRootArea().registerExtensionPoint(ExtensionPoints.ERROR_HANDLER, ErrorReportSubmitter.class.getName());
+    Extensions.getRootArea().getExtensionPoint(ExtensionPoints.ERROR_HANDLER).registerExtension(new ITNReporter());
   }
 
   public static boolean shouldLoadPlugins() {

source/com/intellij/openapi/components/impl/ComponentManagerImpl.java

@@ -1,5 +1,6 @@
 package com.intellij.openapi.components.impl;
 
+import com.intellij.ExtensionPoints;
 import com.intellij.diagnostic.PluginException;
 import com.intellij.ide.plugins.ComponentDescriptor;
 import com.intellij.ide.plugins.PluginDescriptor;
@@ -375,7 +376,7 @@ public abstract class ComponentManagerImpl extends UserDataHolderBase implements
     if (ApplicationManagerEx.getApplicationEx().isUnitTestMode()) return; // TODO: quick and dirty. To make tests running.
     
     final ComponentDescriptor[] componentDescriptors =
-      (ComponentDescriptor[])extensionsArea.getExtensionPoint(PluginManager.COMPONENT_EXTENSION_POINT).getExtensions();
+      (ComponentDescriptor[])extensionsArea.getExtensionPoint(ExtensionPoints.COMPONENT).getExtensions();
     for (int i = 0; i < componentDescriptors.length; i++) {
       ComponentDescriptor descriptor = componentDescriptors[i];
       final Map<String, String> options = descriptor.getOptionsMap();