Use 64kb read buffer in CRNHttpProtocolHandler on iOS.

components/cronet/ios/test/test_server.h

Index: components/cronet/ios/test/test_server.h
diff --git a/components/cronet/ios/test/test_server.h b/components/cronet/ios/test/test_server.h
index 4804f24cbf5b5586f70a9d6e304c8d230d78a633..0fa6aa99f2be7e77243d0bb22c0a169b4ec6b473 100644
--- a/components/cronet/ios/test/test_server.h
+++ b/components/cronet/ios/test/test_server.h
@@ -20,6 +20,8 @@ class TestServer {
   // Returns URL which respond with setting cookie to |cookie_line| and echo it
   // in response body.
   static std::string GetSetCookieURL(const std::string& cookie_line);
+  // Returns URL which respond with |data_size| of bytes in response body.
+  static std::string GetBigDataURL(long data_size);
 };
 
 }  // namespace cronet