[ReactNative] Maintain order of bridge calls

Summary:
When bridge calls are made, they should be dispatched to their
destination GCD queue in the same order they were made. (It
looks like this invariant broke in 336e18d, which caused call
order to depend on the iteration of `NSMapTable` keys
whenever there are calls to multiple modules that share a queue)

Fixes #1941 (in which RCTUIManager createView addUIBlock
blocks were sometimes running after other blocks that depended
on them)

I'm a react-native/iOS/objc newbie, so please excuse any
ignorance this commit may well contain :)
Closes https://github.com/facebook/react-native/pull/2488
Github Author: Ted Suzman <ted@suzman.net>

React/Base/RCTBatchedBridge.m

@@ -664,22 +664,23 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
       // verify that class has been registered
       (void)_modulesByName[moduleData.name];
     }
-    NSMutableOrderedSet *set = [buckets objectForKey:moduleData];
+    id queue = [moduleData queue];
+    NSMutableOrderedSet *set = [buckets objectForKey:queue];
     if (!set) {
       set = [NSMutableOrderedSet new];
-      [buckets setObject:set forKey:moduleData];
+      [buckets setObject:set forKey:queue];
     }
     [set addObject:@(i)];
   }
 
-  for (RCTModuleData *moduleData in buckets) {
+  for (id queue in buckets) {
     RCTProfileBeginFlowEvent();
 
-    [moduleData dispatchBlock:^{
+    dispatch_block_t block = ^{
       RCTProfileEndFlowEvent();
       RCTProfileBeginEvent(0, RCTCurrentThreadName(), nil);
 
-      NSOrderedSet *calls = [buckets objectForKey:moduleData];
+      NSOrderedSet *calls = [buckets objectForKey:queue];
       @autoreleasepool {
         for (NSNumber *indexObj in calls) {
           NSUInteger index = indexObj.unsignedIntegerValue;
@@ -693,7 +694,13 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
       RCTProfileEndEvent(0, @"objc_call,dispatch_async", @{
         @"calls": @(calls.count),
       });
-    }];
+    };
+
+    if (queue == RCTJSThread) {
+      [_javaScriptExecutor executeBlockOnJavaScriptQueue:block];
+    } else if (queue) {
+      dispatch_async(queue, block);
+    }
   }
 
   // TODO: batchDidComplete is only used by RCTUIManager - can we eliminate this special case?