feat(webSocket): Add binaryType to config object

Add binaryType to config object, so that it is possible
to set that parameter on underlying socket before any
data emits happen.

Closes #2353

spec/observables/dom/webSocket-spec.ts

@@ -261,6 +261,20 @@ describe('Observable.webSocket', () => {
       subject.unsubscribe();
     });
 
+    it('should take a binaryType and set it properly on the web socket', () => {
+      const subject = Observable.webSocket({
+        url: 'ws://mysocket',
+        binaryType: 'blob'
+      });
+
+      subject.subscribe();
+
+      const socket = MockWebSocket.lastSocket;
+      expect(socket.binaryType).to.equal('blob');
+
+      subject.unsubscribe();
+    });
+
     it('should take a resultSelector', () => {
       const results = [];
 
@@ -632,6 +646,7 @@ class MockWebSocket {
   readyState: number = 0;
   closeCode: any;
   closeReason: any;
+  binaryType?: string;
 
   constructor(public url: string, public protocol: string) {
     MockWebSocket.sockets.push(this);

src/observable/dom/WebSocketSubject.ts

@@ -18,6 +18,7 @@ export interface WebSocketSubjectConfig {
   closeObserver?: NextObserver<CloseEvent>;
   closingObserver?: NextObserver<void>;
   WebSocketCtor?: { new(url: string, protocol?: string|Array<string>): WebSocket };
+  binaryType?: 'blob' | 'arraybuffer';
 }
 
 /**
@@ -34,6 +35,7 @@ export class WebSocketSubject<T> extends AnonymousSubject<T> {
   closeObserver: NextObserver<CloseEvent>;
   closingObserver: NextObserver<void>;
   WebSocketCtor: { new(url: string, protocol?: string|Array<string>): WebSocket };
+  binaryType?: 'blob' | 'arraybuffer';
 
   private _output: Subject<T>;
 
@@ -159,6 +161,9 @@ export class WebSocketSubject<T> extends AnonymousSubject<T> {
         new WebSocketCtor(this.url, this.protocol) :
         new WebSocketCtor(this.url);
       this.socket = socket;
+      if (this.binaryType) {
+        this.socket.binaryType = this.binaryType;
+      }
     } catch (e) {
       observer.error(e);
       return;