Add a diagnostic.getServerPort analysis server request.

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 d9213e2333e7d6d4bc662b39c4ce39fd3d116447..0c0c91254b07b0cf38ee55623c0fe87370c171d3 100644
--- a/pkg/analysis_server/tool/spec/spec_input.html
+++ b/pkg/analysis_server/tool/spec/spec_input.html
@@ -2049,6 +2049,19 @@
           </field>
         </result>
       </request>
+      <request method="getServerPort">
+        <p>
+          Return the port of the diagnostic web server. If the server is not running
+          this call will start the server. If unable to start the diagnostic web server,
+          this call will return an error of ERROR_HANDLING_REQUEST.
+        </p>
+        <result>
+          <field name="port">
+            <ref>int</ref>
+            <p>The diagnostic server port.</p>
+          </field>
+        </result>
+      </request>
     </domain>
     <types>
       <h2 class="domain"><a name="types">Types</a></h2>
@@ -3840,6 +3853,12 @@
             </p>
           </value>
           <value>
+            <code>ERROR_HANDLING_REQUEST</code>

[Brian Wilkerson, 2017/02/18 21:41:03]

This is too general; all existing and future errors could be replaced by this.
:-) Error codes are more useful if they carry some semantic value. (Otherwise
there's no point in having an error code.) Perhaps this could be something like
"DEBUG_PORT_COULD_NOT_BE_OPENED".

Also, we keep enum values alphabetized in their lists.

[devoncarew, 2017/02/19 02:43:05]

:) It did seem a bit general when I was writing it.
DEBUG_PORT_COULD_NOT_BE_OPENED sgtm; updated, and adjusted the position to sort
correctly.

+            <p>
+              The server was unable to handle the request.
+            </p>
+          </value>
+          <value>
             <code>SERVER_ALREADY_STARTED</code>
             <p>
               The analysis server has already been started (and hence