Update manager fixes to handle update check failures.

editor/tools/plugins/com.google.dart.tools.update.core/src/com/google/dart/tools/update/core/internal/jobs/CheckForUpdatesJob.java

Index: editor/tools/plugins/com.google.dart.tools.update.core/src/com/google/dart/tools/update/core/internal/jobs/CheckForUpdatesJob.java
===================================================================
--- editor/tools/plugins/com.google.dart.tools.update.core/src/com/google/dart/tools/update/core/internal/jobs/CheckForUpdatesJob.java	(revision 9083)
+++ editor/tools/plugins/com.google.dart.tools.update.core/src/com/google/dart/tools/update/core/internal/jobs/CheckForUpdatesJob.java	(working copy)
@@ -31,6 +31,7 @@
 
   private final DownloadManager downloadManager;
   private Revision latest;
+  private String message;
 
   /**
    * Create an instance.
@@ -43,6 +44,15 @@
   }
 
   /**
+   * Get details in case an error occurred during check for updates.
+   * 
+   * @return the message a displayable error message (or <code>null</code> if none was recorded)
+   */
+  public String getErrorMessage() {
+    return message;
+  }
+
+  /**
    * Get the latest available update.
    * 
    * @return the latest update, or <code>null</code> if it has not been retrieved yet
@@ -56,7 +66,8 @@
     try {
       latest = downloadManager.getLatestRevision();
     } catch (IOException e) {
-      return UpdateCore.createErrorStatus("Unable to get latest revision: " + e.getMessage()); //$NON-NLS-1$
+      message = "Unable to get latest revision.";
+      UpdateCore.logError(message);//$NON-NLS-1$
     }
     return Status.OK_STATUS;
   }