Removed fixed dependencies

packages/plugin/notes.txt

+--------------------------------------------------------------------------------
+
+To provide a psuedo backward compatible layer.
+
+In plugin.dart:
+
+/**
+ * A function used to register an extension point with the given simple
+ * [identifier]. If given, the [validator] will be used to validate extensions
+ * to the extension point.
+ *
+ * An [ExtensionError] will be thrown if the extension point cannot be
+ * registered, such as when a plugin attempts to define two extension points
+ * with the same simple identifier.
+ */
+typedef ExtensionPoint RegisterExtensionPoint(String identifier,
+    [ValidateExtension validateExtension]);
+
+class Plugin {
+  /**
+   * Use the [register] function to register all of the extension points
+   * contributed by this plugin.
+   *
+   * Clients should not invoke the [register] function after this method has
+   * returned.
+   *
+   * This method is deprecated and will be removed in the next breaking release.
+   * Plugins should migrate to using [registerExtensionPoints2].
+   */
+  void registerExtensionPoints(RegisterExtensionPoint register);
+}
+
+In plugin_impl.dart:
+
+class ExtensionManager {
+
+  In processPlugins:
+
+      for (Plugin plugin in plugins) {
+        plugin.registerExtensionPoints((String identifier,
+            [ValidateExtension validateExtension]) =>
+          registerExtensionPoint(plugin, identifier, validateExtension));
+      }
+
+  /**
+   * Register an extension point being defined by the given [plugin] with the
+   * given simple [identifier] and [validateExtension].
+   */
+  ExtensionPoint registerExtensionPoint(
+        Plugin plugin, String identifier, ValidateExtension validateExtension) {
+    String uniqueIdentifier = Plugin.buildUniqueIdentifier(plugin, identifier);
+    if (extensionPoints.containsKey(uniqueIdentifier)) {
+      throw new ExtensionError(
+            'There is already an extension point with the id "$identifier"');
+    }
+    ExtensionPointImpl extensionPoint =
+          new ExtensionPointImpl(plugin, identifier, validateExtension);
+    extensionPoints[uniqueIdentifier] = extensionPoint;
+    return extensionPoint;
+  }
+}
+
+--------------------------------------------------------------------------------