Release Android Preview 21 and bilingual changelog

Add permission-based reading of Android contacts, SMS and call history. Include shared Gaia fixes and document device validation limits. Pixel image qualification remains pending.

android/tools/rdp.py

@@ -29,6 +29,8 @@ class RDP:
         while True:
             r = self.recv()
             self.events.append(r)
+            if str(r.get("type", "")).endswith("ListChanged"):
+                continue
             if r.get("from") == to and (r.get("type") not in ["consoleAPICall", "pageError"]):
                 return r