Add the 'cache' datatype to the clear-site-data WPT

third_party/WebKit/LayoutTests/external/wpt/clear-site-data/support/test_utils.js

 var TestUtils = (function() {
   function randomString() {
     var result = "";
     for (var i = 0; i < 5; i++)
         result += String.fromCharCode(97 + Math.floor(Math.random() * 26));
     return result;
   };
 
+  /** @string The base URL this test. */
+  var base_url = location.origin + "/clear-site-data/";

[Mike West, 2017/05/30 07:45:17]

Can you add cross-origin tests as well, since I think that's the use case folks
internally are most interested in?

[msramek, 2017/05/30 09:11:12]

Of course, but I'd like to do that in a separate CL. This one was intended to
finalize the list of datatypes in TestUtils (which will be retrieved by all
tests).

[Mike West, 2017/05/30 11:01:30]

Sure. Happy to see more CLs. :)

+
   /**
    * Representation of one datatype.
    * @typedef Datatype
    * @type{object}
    * @property{string} name Name of the datatype.
    * @method{function():Void} add A function to add an instance of the datatype.
    * @method{function():boolean} isEmpty A function that tests whether
    *     the datatype's storage backend is empty.
    */
   var Datatype;
@@ skipping 25 matching lines @@
         return new Promise(function(resolve, reject) {
           localStorage.setItem(randomString(), randomString());
           resolve();
         });
       },
       "isEmpty": function() {
         return new Promise(function(resolve, reject) {
           resolve(!localStorage.length);
         });
       }
-    }
+    },
+    {
+      "name": "cache",
+      "add": function() {
+        // Request a resource from the get_resource_to_cache.py server.
+        // The server is instructed to return a high "CacheControl: max-age"

[Mike West, 2017/05/30 07:45:17]

Nit: `cache-control`

[msramek, 2017/05/30 09:11:12]

Done. Also capitalized it here and elsewhere for consistency (internal and with
e.g. https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Cache-Control).
And verified that the request class in the python server performs "in" and []
operations in a case-insensitive way.

+        // header value, to ensure that this resource will really be added
+        // to the cache.
+        return fetch(base_url + "support/get-resource-to-cache.py");
+      },
+      "isEmpty": function() {
+        return new Promise(function(resolve, reject) {
+          // Request the resource with the "Cache-Control: only-if-cached"
+          // header. If the request suceeds, the resource must have been found
+          // in the cache. Since not all user agents support this header value,
+          // the get-resource-to-cache.py server is instructed to respond with
+          // status code 500 if it sees such a request.
+          var fetch_options = {
+            "headers": new Headers({ "cache-control": "only-if-cached" }),
+          };
+
+          fetch(base_url + "support/get-resource-to-cache.py", fetch_options)
+              .then(function(response) {
+                resolve(response.status == 500  /* Internal server error. */);
+              }).catch(function() {
+                resolve(true);

[Mike West, 2017/05/30 07:45:17]

Why would you resolve with `true` if the fetch failed?

[msramek, 2017/05/30 09:11:12]

If the fetch fails, it means that we're dealing with a user agent that supports
"only-if-cached" and didn't find the resource in cache, which means that
"isEmpty()" is true.

[Mike West, 2017/05/30 11:01:31]

Ah. I see. A comment to that effect might be helpful, as I'd missed it. (Also,
does `only-if-cached` work cross-origin? I don't think it does...)

Have you run the test in Firefox to confirm that it fails?

+              });
+        });
+      }
+    },
   ];
 
   /**
    * All possible combinations of datatypes.
    * @property {Array.<Array.<Datatype>>}
    */
   TestUtils.COMBINATIONS = (function() {
     var combinations = [];
     for (var mask = 0; mask < (1 << TestUtils.DATATYPES.length); mask++) {
       var combination = [];
@@ skipping 10 matching lines @@
   })();
 
   /**
    * Get the support server URL that returns a Clear-Site-Data header
    * to clear |datatypes|.
    * @param{Array.<Datatype>} datatypes The list of datatypes to be deleted.
    * @return string The URL to be queried.
    */
   TestUtils.getClearSiteDataUrl = function(datatypes) {
     names = datatypes.map(function(e) { return e.name });
-    return "support/echo-clear-site-data.py?" + names.join("&");
+    return base_url + "support/echo-clear-site-data.py?" + names.join("&");
   }
 
   return TestUtils;
 })();