[Bindings] Make maplike<> and setlike<> imply a readonly size attribute.

content/shell/test_runner/mock_webrtc_peer_connection_handler.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/shell/test_runner/mock_webrtc_peer_connection_handler.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 215 matching lines @@
         return std::unique_ptr<blink::WebRTCStats>(new MockWebRTCStats(stats));
     }
     return nullptr;
   }
   std::unique_ptr<blink::WebRTCStats> Next() override {
     if (i_ >= stats_.size())
       return nullptr;
     return std::unique_ptr<blink::WebRTCStats>(
         new MockWebRTCStats(stats_[i_++]));
   }
+  size_t Size() const override { return stats_.size(); }
 
  private:
   std::vector<MockWebRTCStats> stats_;
   size_t i_;
 };
 
 class MockWebRTCRtpContributingSource
     : public blink::WebRTCRtpContributingSource {
  public:
   MockWebRTCRtpContributingSource(
@@ skipping 428 matching lines @@
     const WebMediaStreamTrack& track) {
   return new MockWebRTCDTMFSenderHandler(track, interfaces_->GetDelegate());
 }
 
 void MockWebRTCPeerConnectionHandler::Stop() {
   stopped_ = true;
   weak_factory_.InvalidateWeakPtrs();
 }
 
 }  // namespace test_runner