Tighter native type annotations for some elements returning Lists

tools/dom/scripts/dartmetadata.py

Index: tools/dom/scripts/dartmetadata.py
diff --git a/tools/dom/scripts/dartmetadata.py b/tools/dom/scripts/dartmetadata.py
index 928c1ccbd7137c16291db839ea7749e5406ecbec..c25100ac08deb0fd77af7e0c1f3d11a93a1c44c7 100644
--- a/tools/dom/scripts/dartmetadata.py
+++ b/tools/dom/scripts/dartmetadata.py
@@ -83,6 +83,11 @@ _dart2js_annotations = monitored.Dict('dartmetadata._dart2js_annotations', {
       "@Creates('Null')",
     ],
 
+    'Element.webkitGetRegionFlowRanges': [
+      "@Creates('JSExtendableArray')",
+      "@Returns('JSExtendableArray')",
+    ],
+
     "ErrorEvent.error": [
       "@Creates('Null')", # Only returns values created elsewhere.
     ],
@@ -202,6 +207,16 @@ _dart2js_annotations = monitored.Dict('dartmetadata._dart2js_annotations', {
       "@Returns('int|String|Null')",
     ],
 
+    'MediaStream.getAudioTracks': [
+      "@Creates('JSExtendableArray')",
+      "@Returns('JSExtendableArray')",
+    ],
+
+    'MediaStream.getVideoTracks': [
+      "@Creates('JSExtendableArray')",
+      "@Returns('JSExtendableArray')",
+    ],
+
     'MessageEvent.data': [
       "@annotation_Creates_SerializedScriptValue",
       "@annotation_Returns_SerializedScriptValue",