Minor clean-up and bug fix

pkg/analysis_server/lib/src/plugin/plugin_locator.dart

Index: pkg/analysis_server/lib/src/plugin/plugin_locator.dart
diff --git a/pkg/analysis_server/lib/src/plugin/plugin_locator.dart b/pkg/analysis_server/lib/src/plugin/plugin_locator.dart
index 85e3527fe83177a580d7e6240fbc1e41d6108ed0..acd319937a9de6b3e8f41a8b9799925ea7c70348 100644
--- a/pkg/analysis_server/lib/src/plugin/plugin_locator.dart
+++ b/pkg/analysis_server/lib/src/plugin/plugin_locator.dart
@@ -51,8 +51,14 @@ class PluginLocator {
    * associated with the package.
    *
    * This will look first in the `pubspec.yaml` file in the package root for a
-   * key indicating where the plugin is located. If such a key is not defined,
-   * then it will fall back to a well known location within the package.
+   * top-level key (`analysis_plugin`) indicating where the plugin is located.
+   * The value associated with the key is expected to be the path of the plugin
+   * relative to the package root. If the directory exists, the it is returned.
+   *
+   * If the key is not defined in the `pubspec.yaml` file, or if the directory
+   * given does not exist, then this method will look for the directory
+   * `tools/analysis_plugin` relative to the package root. If the directory
+   * exists, the it is returned.

[scheglov, 2017/04/24 15:33:55]

/the/then/s

[Brian Wilkerson, 2017/04/24 15:48:51]

Done

    *
    * This method does not validate the content of the plugin directory before
    * returning it.