Update documentation to clarify AppCache usage

Bug: 5869022
Change-Id: I46abecfb0e8975cc924458f444f95cdabaa3f712
diff --git a/core/java/android/webkit/WebStorage.java b/core/java/android/webkit/WebStorage.java
index 76674f4..1e955bd 100644
--- a/core/java/android/webkit/WebStorage.java
+++ b/core/java/android/webkit/WebStorage.java
@@ -23,17 +23,22 @@
  * {@link WebView}. It manages the Application Cache API, the Web SQL Database
  * API and the HTML5 Web Storage API.
  *
- * The Web SQL Database API provides storage which is private to a given
- * origin, where an origin comprises the host, scheme and port of a URI.
- * Similarly, use of the Application Cache API can be attributed to an origin.
- * This class provides access to the storage use and quotas for these APIs for
- * a given origin. Origins are represented using {@link WebStorage.Origin}.
+ * The Application Cache API provides a mechanism to create and maintain an
+ * application cache to power offline Web applications. Use of the Application
+ * Cache API can be attributed to an origin {@link WebStorage.Origin}, however
+ * it is not possible to set per-origin quotas. Note that there can be only
+ * one application cache per application.
+ *
+ * The Web SQL Database API provides storage which is private to a given origin.
+ * Similar to the Application Cache, use of the Web SQL Database can be attributed
+ * to an origin. It is also possible to set per-origin quotas.
  */
 public class WebStorage {
 
     /**
      * Encapsulates a callback function which is used to provide a new quota
-     * for a JavaScript storage API. See
+     * for a JavaScript storage API.
+     * See
      * {@link WebChromeClient#onExceededDatabaseQuota} and
      * {@link WebChromeClient#onReachedMaxAppCacheSize}.
      */
@@ -54,6 +59,7 @@
     /**
      * This class encapsulates information about the amount of storage
      * currently used by an origin for the JavaScript storage APIs.
+     * An origin comprises the host, scheme and port of a URI.
      * See {@link WebStorage} for details.
      */
     public static class Origin {