WebSocket polyfill

Summary:
- Added as a library in /Libraries/WebSocket
- Drag and drop to add to project (similar to adding Geolocation polyfill)
- Exposed as `window.WebSocket` which conforms with https://developer.mozilla.org/en-US/docs/Web/API/WebSocket specs
Closes https://github.com/facebook/react-native/pull/890
Github Author: Harrison Harnisch <hharnisc@gmail.com>

Test Plan: Imported from GitHub, without a `Test Plan:` line.

Libraries/WebSocket/RCTWebSocketManager.m

@@ -0,0 +1,116 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+#import "RCTWebSocketManager.h"
+
+#import "RCTBridge.h"
+#import "RCTEventDispatcher.h"
+#import "RCTSRWebSocket.h"
+#import "RCTSparseArray.h"
+
+@implementation RCTSRWebSocket (React)
+
+- (NSNumber *)reactTag
+{
+  return objc_getAssociatedObject(self, _cmd);
+}
+
+- (void)setReactTag:(NSNumber *)reactTag
+{
+  objc_setAssociatedObject(self, @selector(reactTag), reactTag, OBJC_ASSOCIATION_COPY_NONATOMIC);
+}
+
+@end
+
+@interface RCTWebSocketManager () <RCTSRWebSocketDelegate>
+
+@end
+
+@implementation RCTWebSocketManager
+{
+    RCTSparseArray *_sockets;
+}
+
+RCT_EXPORT_MODULE()
+
+@synthesize bridge = _bridge;
+
+- (instancetype)init
+{
+  if ((self = [super init])) {
+    _sockets = [[RCTSparseArray alloc] init];
+  }
+  return self;
+}
+
+- (void)dealloc
+{
+  for (RCTSRWebSocket *socket in _sockets.allObjects) {
+    socket.delegate = nil;
+    [socket close];
+  }
+}
+
+RCT_EXPORT_METHOD(connect:(NSURL *)URL socketID:(NSNumber *)socketID)
+{
+  RCTSRWebSocket *webSocket = [[RCTSRWebSocket alloc] initWithURL:URL];
+  webSocket.delegate = self;
+  webSocket.reactTag = socketID;
+  _sockets[socketID] = webSocket;
+  [webSocket open];
+}
+
+RCT_EXPORT_METHOD(send:(NSString *)message socketID:(NSNumber *)socketID)
+{
+  [_sockets[socketID] send:message];
+}
+
+RCT_EXPORT_METHOD(close:(NSNumber *)socketID)
+{
+  [_sockets[socketID] close];
+  _sockets[socketID] = nil;
+}
+
+#pragma mark - RCTSRWebSocketDelegate methods
+
+- (void)webSocket:(RCTSRWebSocket *)webSocket didReceiveMessage:(id)message
+{
+  [_bridge.eventDispatcher sendDeviceEventWithName:@"websocketMessage" body:@{
+    @"data": message,
+    @"id": webSocket.reactTag
+  }];
+}
+
+- (void)webSocketDidOpen:(RCTSRWebSocket *)webSocket
+{
+  [_bridge.eventDispatcher sendDeviceEventWithName:@"websocketOpen" body:@{
+    @"id": webSocket.reactTag
+  }];
+}
+
+- (void)webSocket:(RCTSRWebSocket *)webSocket didFailWithError:(NSError *)error
+{
+  [_bridge.eventDispatcher sendDeviceEventWithName:@"websocketFailed" body:@{
+    @"message":[error localizedDescription],
+    @"id": webSocket.reactTag
+  }];
+}
+
+- (void)webSocket:(RCTSRWebSocket *)webSocket didCloseWithCode:(NSInteger)code
+           reason:(NSString *)reason wasClean:(BOOL)wasClean
+{
+  [_bridge.eventDispatcher sendDeviceEventWithName:@"websocketClosed" body:@{
+    @"code": @(code),
+    @"reason": reason,
+    @"clean": @(wasClean),
+    @"id": webSocket.reactTag
+  }];
+}
+
+@end