feat(Network): introduce response.securityDetails() method (#1880)

This patch:
- introduces `SecurityDetails` class that exposes a set of fields that describe properties of secure connection
- introduces method `response.securityDetails()` that returns an instance of `SecurityDetails` object.

lib/NetworkManager.js

@@ -253,7 +253,7 @@ class NetworkManager extends EventEmitter {
     if (!request)
       return;
     const response = new Response(this._client, request, event.response.status, event.response.headers,
-        event.response.fromDiskCache, event.response.fromServiceWorker);
+        event.response.fromDiskCache, event.response.fromServiceWorker, event.response.securityDetails);
     request._response = response;
     this.emit(NetworkManager.Events.Response, response);
   }
@@ -498,10 +498,11 @@ class Response {
    * @param {!Request} request
    * @param {number} status
    * @param {!Object} headers
+   * @param {!Object} securityDetails
    * @param {boolean} fromDiskCache
    * @param {boolean} fromServiceWorker
    */
-  constructor(client, request, status, headers, fromDiskCache, fromServiceWorker) {
+  constructor(client, request, status, headers, fromDiskCache, fromServiceWorker, securityDetails = null) {
     this._client = client;
     this._request = request;
     this._contentPromise = null;
@@ -513,6 +514,15 @@ class Response {
     this._headers = {};
     for (const key of Object.keys(headers))
       this._headers[key.toLowerCase()] = headers[key];
+    this._securityDetails = {};
+    if (securityDetails) {
+      this._securityDetails = new SecurityDetails(
+          securityDetails['subjectName'],
+          securityDetails['issuer'],
+          securityDetails['validFrom'],
+          securityDetails['validTo'],
+          securityDetails['protocol']);
+    }
   }
 
   /**
@@ -543,6 +553,13 @@ class Response {
     return this._headers;
   }
 
+  /**
+   * @return {!SecurityDetails|Object}
+   */
+  securityDetails() {
+    return this._securityDetails;
+  }
+
   /**
    * @return {!Promise<!Buffer>}
    */
@@ -631,6 +648,59 @@ function generateRequestHash(request) {
   return JSON.stringify(hash);
 }
 
+class SecurityDetails {
+  /**
+   * @param {string} subjectName
+   * @param {string} issuer
+   * @param {number} validFrom
+   * @param {number} validTo
+   * @param {string} protocol
+   */
+
+  constructor(subjectName, issuer, validFrom, validTo, protocol) {
+    this._subjectName = subjectName;
+    this._issuer = issuer;
+    this._validFrom = validFrom;
+    this._validTo = validTo;
+    this._protocol = protocol;
+  }
+
+  /**
+   * @return {string}
+   */
+  subjectName() {
+    return this._subjectName;
+  }
+
+  /**
+   * @return {string}
+   */
+  issuer() {
+    return this._issuer;
+  }
+
+  /**
+   * @return {number}
+   */
+  validFrom() {
+    return this._validFrom;
+  }
+
+  /**
+   * @return {number}
+   */
+  validTo() {
+    return this._validTo;
+  }
+
+  /**
+   * @return {string}
+   */
+  protocol() {
+    return this._protocol;
+  }
+}
+
 NetworkManager.Events = {
   Request: 'request',
   Response: 'response',