added RCTTouchEvent (5/7)

Summary:
This diff adds an implementation of `RCTEvent` protocol which represents touch events.
It's basically a copy of this code: c14cc123d5/React/Base/RCTTouchHandler.m (L194-L196)
which is replaced using `RCTTouchEvent` in the next diff (D2884593).

public
___
//This diff is part of a larger stack. For high level overview what's going on jump to D2884593.//

Reviewed By: nicklockwood

Differential Revision: D2884592

fb-gh-sync-id: e35addcf15a7012f89644200a08f5856c7f57299

React/Base/RCTTouchEvent.h

@@ -0,0 +1,23 @@
+/**
+ * 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 <Foundation/Foundation.h>
+
+#import "RCTEventDispatcher.h"
+
+/**
+ * Represents a touch event, which may be composed of several touches (one for every finger).
+ * For more information on contents of passed data structures see RCTTouchHandler.
+ */
+@interface RCTTouchEvent : NSObject <RCTEvent>
+
+- (instancetype)initWithEventName:(NSString *)eventName
+                     reactTouches:(NSArray<NSDictionary *> *)reactTouches
+                   changedIndexes:(NSArray<NSNumber *> *)changedIndexes NS_DESIGNATED_INITIALIZER;
+@end

React/Base/RCTTouchEvent.m

@@ -0,0 +1,57 @@
+/**
+ * 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 "RCTTouchEvent.h"
+
+@implementation RCTTouchEvent
+{
+  NSArray<NSDictionary *> *_reactTouches;
+  NSArray<NSNumber *> *_changedIndexes;
+}
+
+@synthesize eventName = _eventName;
+@synthesize viewTag = _viewTag;
+
+- (instancetype)initWithEventName:(NSString *)eventName
+                     reactTouches:(NSArray<NSDictionary *> *)reactTouches
+                   changedIndexes:(NSArray<NSNumber *> *)changedIndexes
+{
+  if (self = [super init]) {
+    _eventName = eventName;
+    _reactTouches = reactTouches;
+    _changedIndexes = changedIndexes;
+  }
+  return self;
+}
+
+RCT_NOT_IMPLEMENTED(- (instancetype)init)
+
+#pragma mark - RCTEvent
+
+- (BOOL)canCoalesce
+{
+  return NO;
+}
+
+- (id<RCTEvent>)coalesceWithEvent:(id<RCTEvent>)newEvent
+{
+  return newEvent;
+}
+
++ (NSString *)moduleDotMethod
+{
+  return @"RCTEventEmitter.receiveTouches";
+}
+
+- (NSArray *)arguments
+{
+  return @[RCTNormalizeInputEventName(_eventName), _reactTouches, _changedIndexes];
+}
+
+@end