Return operation name in prefetch request callback and add internal page hookup

chrome/browser/resources/offline_pages/offline_internals.html

Index: chrome/browser/resources/offline_pages/offline_internals.html
diff --git a/chrome/browser/resources/offline_pages/offline_internals.html b/chrome/browser/resources/offline_pages/offline_internals.html
index b045ae6fbea029bf3974c078fb55ea513b1b1036..5ec5858dc845fe4c9c0ebfbbdc1c84b8c91fef89 100644
--- a/chrome/browser/resources/offline_pages/offline_internals.html
+++ b/chrome/browser/resources/offline_pages/offline_internals.html
@@ -85,6 +85,14 @@
         <button id="schedule-nwake">Schedule NWake</button>
         <button id="cancel-nwake">Cancel NWake</button>
       </div>
+      <div>
+        <div>
+          <input id="request-data" type="text">

[dewittj, 2017/06/12 18:31:04]

There should be different input boxes for the two types of operation, and at
least a tiny bit of info about what to put here.

GeneratePageBundle: "A list of URLs, separated by spaces"
GetOperation: "An operation name returned by GeneratePageBundle"

I'd also like to see more structured output for GeneratePageBundle, something
readable on mobile.  That can be left for a future change, but please add an
Asana task or a bug for it.

[jianli, 2017/06/12 22:40:30]

Added 2nd input box. Added explanation for input box values. Also made the
output more structured.

+        </div>
+        <button id="generate-page-bundle">Generate Page Bundle</button>
+        <button id="get-operation">Get Operation</button>
+      </div>
     </div>
+    <div id="prefetch-actions-info"></div>

[dewittj, 2017/06/12 18:31:04]

This should probably have different formatting that preserves whitespace.  maybe
style="white-space: pre-wrap"?

[jianli, 2017/06/12 22:40:30]

Done.

   </body>
 </html>