Trivial exportable change in wpt.

third_party/WebKit/LayoutTests/external/wpt/referrer-policy/README.md

 # Referrer-Policy Web Platform Tests
 
 The Referrer-Policy tests are designed for testing browser implementations and conformance to the [W3 Referrer-Policy Specification](http://w3c.github.io/webappsec/specs/referrer-policy/).
 
 ## Project structure
 
 The project contains tools, templates and a seed (```spec.src.json```) for generating tests. The main assertion logic resides in JS files in the root of the ```./generic/``` directory.
 
 This is the overview of the project structure:
 
@@ skipping 196 matching lines @@
       ]
     }
 ```
 
 **NOTE:** An expansion is always constructive (inclusive), there isn't a negation operator for explicit exclusion. Be aware that using an empty list ```[]``` matches (expands into) exactly nothing. Tests which are to be excluded should be defined in the ```excluded_tests``` section instead.
 
 A single test expansion pattern, be it a requirement or a suppressed pattern, gets expanded into a list of **selections** as follows:
 
 * Expand each field's pattern (single, any of, or all) to list of allowed values (defined by the ```test_expansion_schema```)
 
-* Permute - Recursively enumerate all **selections** accross all fields
+* Permute - Recursively enumerate all **selections** across all fields
 
 Be aware that if there is more than one pattern expanding into a same selection (which also shares the same ```name``` field), the pattern appearing later in the spec JSON will overwrite a previously generated selection. To make sure this is not undetected when generating, set the value of the ```expansion``` field to ```default``` for an expansion appearing earlier and ```override``` for the one appearing later.
 
 A **selection** is a single **test instance** (scenario) with explicit values, for example:
 
 ```javascript
 var scenario = {
   "referrer_policy": "origin-when-cross-origin",
   "delivery_method": "meta-referrer",
   "redirection": "no-redirect",
   "origin": "cross-origin",
   "source_protocol": "http",
   "target_protocol": "http",
   "subresource": "iframe-tag",
   "subresource_path": "/referrer-policy/generic/subresource/document.py",
   "referrer_url": "origin"
 };
 ```
 
 Essentially, this is what gets generated and defines a single test. The scenario is then evaluated by the ```ReferrerPolicyTestCase``` in JS. For the rest of the arranging part, see the ```./generic/template/``` directory and examine ```./generic/tools/generate.py``` to see how the values for the templates are produced.
 
 
 Taking the spec JSON, the generator follows this algorithm:
 
 * Expand all ```excluded_tests``` to create a blacklist of selections
 
 * For each specification requirement: Expand the ```test_expansion``` pattern into selections and check each against the blacklist, if not marked as suppresed, generate the test resources for the selection