[Fetch API] Implement combining of Headers with same keys.

third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/headers.js

Index: third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/headers.js
diff --git a/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/headers.js b/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/headers.js
index a87a75febb4649089b93afcb12235d1a2b5a4113..9ba994c1063441ea8c42a106e7e58b64957def9a 100644
--- a/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/headers.js
+++ b/third_party/WebKit/LayoutTests/http/tests/fetch/script-tests/headers.js
@@ -239,6 +239,8 @@ test(function(t) {
     headers.set('a', '1');
     headers.set('b', '2');
     headers.set('c', '3');
+    headers.append('a', '2');
+    headers.append('a', '3');
 
     const iterator = headers.entries();
 
@@ -246,11 +248,15 @@ test(function(t) {
     headers.set('d', '4');
 
     const keys = [];
-    for (let [key, value] of iterator)
+    for (let [key, value] of iterator){
         keys.push(key);
+        values.push(value);
+      }
     assert_array_equals(keys, ['a', 'b', 'c'],
                         'The pairs to iterate over should be the return ' +
                         'value of an algorithm that implicitly makes a copy.');
+    assert_array_equals(values, ['1,2,3', '2', '3'],
+                        "The values should be combined and seperated by ',' ");

[jsbell, 2016/12/12 21:00:24]

spelling: separated

nit: remove trailing space in string

 }, 'Iteration mutation');
 
 done();