Factor out NetworkID and caching mechanism from n_q_e.{h,cc}

net/nqe/network_quality.h

Index: net/nqe/network_quality.h
diff --git a/net/nqe/network_quality.h b/net/nqe/network_quality.h
index bc1ec771d688d8af0500a1b61265f5941fcb0acf..b06ec7e5b12dd132b632afa38a31005f5c50f1a9 100644
--- a/net/nqe/network_quality.h
+++ b/net/nqe/network_quality.h
@@ -43,6 +43,8 @@ class NET_EXPORT_PRIVATE NetworkQuality {
 
   NetworkQuality& operator=(const NetworkQuality& other);
 
+  bool operator==(const NetworkQuality& other) const;
+
   // Returns the estimate of the round trip time at the HTTP layer.
   const base::TimeDelta& http_rtt() const { return http_rtt_; }