Specify when 'sortMembers' will return an error.

pkg/analysis_server/tool/spec/spec_input.html

Index: pkg/analysis_server/tool/spec/spec_input.html
diff --git a/pkg/analysis_server/tool/spec/spec_input.html b/pkg/analysis_server/tool/spec/spec_input.html
index 107df36aa18d9c4795c9902acc1f4b53450737bb..d7f042596a9b0da53401af8eb0deb864996b7b35 100644
--- a/pkg/analysis_server/tool/spec/spec_input.html
+++ b/pkg/analysis_server/tool/spec/spec_input.html
@@ -1290,6 +1290,15 @@
           Sort all of the directives, unit and class members
           of the given Dart file.
         </p>
+        <p>
+          If a request is made for a file that does not exist, does not belong
+          to an analysis root or is not a Dart file,
+          <tt>SORT_MEMBERS_INVALID_FILE</tt> will be generated.
+        </p>
+        <p>
+          If the Dart file has scan or parse errors,
+          <tt>SORT_MEMBERS_PARSE_ERRORS</tt> will be generated.
+        </p>
         <params>
           <field name="file">
             <ref>FilePath</ref>
@@ -2696,6 +2705,20 @@
             </p>
           </value>
           <value>
+            <code>SORT_MEMBERS_INVALID_FILE</code>
+            <p>
+              An "edit.sortMembers" request specified a FilePath
+              which does not match a Dart file in an analysis root.
+            </p>
+          </value>
+          <value>
+            <code>SORT_MEMBERS_PARSE_ERRORS</code>
+            <p>
+              An "edit.sortMembers" request specified a Dart file that has
+              scan or parse errors.
+            </p>
+          </value>
+          <value>
             <code>UNANALYZED_PRIORITY_FILES</code>
             <p>
               An "analysis.setPriorityFiles" request includes one or