Add [PrefixGet] extended attribute

third_party/WebKit/LayoutTests/fast/dom/idl-dictionary-unittest.html

Index: third_party/WebKit/LayoutTests/fast/dom/idl-dictionary-unittest.html
diff --git a/third_party/WebKit/LayoutTests/fast/dom/idl-dictionary-unittest.html b/third_party/WebKit/LayoutTests/fast/dom/idl-dictionary-unittest.html
index 8170e50fece91f2a4a297c1d8501327a25dc4baf..0c8b1b98264d0fdb8036b090186ecdca7dd68e6c 100644
--- a/third_party/WebKit/LayoutTests/fast/dom/idl-dictionary-unittest.html
+++ b/third_party/WebKit/LayoutTests/fast/dom/idl-dictionary-unittest.html
@@ -37,6 +37,7 @@ if (window.internals && internals.dictionaryTest) {
     shouldBeUndefined('dict.doubleOrStringMember');
     shouldBeUndefined('dict.doubleOrStringSequenceMember');
     shouldBeNull('dict.eventTargetOrNullMember');
+    shouldBeUndefined('dict.prefixGetMember');
     debug('');
 
     debug('Test for setting undefined');
@@ -91,7 +92,8 @@ if (window.internals && internals.dictionaryTest) {
         objectOrNullMemberWithDefault: testObject2,
         doubleOrStringMember: 3.14,
         doubleOrStringSequenceMember: [3.14, 'Hello'],
-        eventTargetOrNullMember: element1
+        eventTargetOrNullMember: element1,
+        prefixGetMember: testObject1,
     });
     dict = dictionaryTest.get();
     shouldBe('dict.longMember', '1');
@@ -120,6 +122,7 @@ if (window.internals && internals.dictionaryTest) {
     shouldBe('dict.doubleOrStringMember', '3.14');
     shouldBe('dict.doubleOrStringSequenceMember', '[3.14, "Hello"]');
     shouldBe('dict.eventTargetOrNullMember', 'element1');
+    shouldBe('dict.prefixGetMember', 'testObject1');
     debug('');
 
     debug('Additional test for union type members');