Avoid dispatch_async in RCTRootView when bridge has already started

Summary:
There's no good reason for initialProperties to be mutable after the RCTRootView has been created. Passing it in through the constructor means we can skip one dispatch_async.

Examples/UIExplorer/UIExplorer/AppDelegate.m

@@ -30,7 +30,8 @@
                                             launchOptions:launchOptions];
 
   RCTRootView *rootView = [[RCTRootView alloc] initWithBridge:bridge
-                                                   moduleName:@"UIExplorerApp"];
+                                                   moduleName:@"UIExplorerApp"
+                                            initialProperties:nil];
 
   self.window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
   UIViewController *rootViewController = [[UIViewController alloc] init];

Examples/UIExplorer/UIExplorerUnitTests/RCTAllocationTests.m

@@ -82,6 +82,7 @@ RCT_EXPORT_METHOD(test:(__unused NSString *)a
   @autoreleasepool {
     RCTRootView *view = [[RCTRootView alloc] initWithBundleURL:nil
                                                     moduleName:@""
+                                             initialProperties:nil
                                                  launchOptions:nil];
     weakBridge = view.bridge;
     XCTAssertNotNil(weakBridge, @"RCTBridge should have been created");
@@ -180,7 +181,7 @@ RCT_EXPORT_METHOD(test:(__unused NSString *)a
                                              launchOptions:nil];
   __weak UIView *rootContentView;
   @autoreleasepool {
-    RCTRootView *rootView = [[RCTRootView alloc] initWithBridge:bridge moduleName:@""];
+    RCTRootView *rootView = [[RCTRootView alloc] initWithBridge:bridge moduleName:@"" initialProperties:nil];
     RUN_RUNLOOP_WHILE(!(rootContentView = [rootView valueForKey:@"contentView"]))
     XCTAssertTrue(rootContentView.userInteractionEnabled, @"RCTContentView should be valid");
     (void)rootView;

Libraries/RCTTest/RCTTestRunner.m

@@ -87,8 +87,7 @@ RCT_NOT_IMPLEMENTED(-init)
                                             moduleProvider:_moduleProvider
                                              launchOptions:nil];
 
-  RCTRootView *rootView = [[RCTRootView alloc] initWithBridge:bridge moduleName:moduleName];
+  RCTRootView *rootView = [[RCTRootView alloc] initWithBridge:bridge moduleName:moduleName initialProperties:initialProps];
-  rootView.initialProperties = initialProps;
   rootView.frame = CGRectMake(0, 0, 320, 2000); // Constant size for testing on multiple devices
 
   NSString *testModuleName = RCTBridgeModuleNameForClass([RCTTestModule class]);

React/Base/RCTRootView.h

@@ -29,7 +29,8 @@ extern NSString *const RCTContentDidAppearNotification;
  * - Designated initializer -
  */
 - (instancetype)initWithBridge:(RCTBridge *)bridge
-                    moduleName:(NSString *)moduleName NS_DESIGNATED_INITIALIZER;
+                    moduleName:(NSString *)moduleName
+             initialProperties:(NSDictionary *)initialProperties NS_DESIGNATED_INITIALIZER;
 
 /**
  * - Convenience initializer -
@@ -40,6 +41,7 @@ extern NSString *const RCTContentDidAppearNotification;
  */
 - (instancetype)initWithBundleURL:(NSURL *)bundleURL
                        moduleName:(NSString *)moduleName
+                initialProperties:(NSDictionary *)initialProperties
                     launchOptions:(NSDictionary *)launchOptions;
 
 /**
@@ -60,7 +62,7 @@ extern NSString *const RCTContentDidAppearNotification;
  * The default properties to apply to the view when the script bundle
  * is first loaded. Defaults to nil/empty.
  */
-@property (nonatomic, copy) NSDictionary *initialProperties;
+@property (nonatomic, copy, readonly) NSDictionary *initialProperties;
 
 /**
  * The class of the RCTJavaScriptExecutor to use with this view.

React/Base/RCTRootView.m

@@ -58,6 +58,7 @@ NSString *const RCTContentDidAppearNotification = @"RCTContentDidAppearNotificat
 
 - (instancetype)initWithBridge:(RCTBridge *)bridge
                     moduleName:(NSString *)moduleName
+             initialProperties:(NSDictionary *)initialProperties
 {
   RCTAssertMainThread();
   RCTAssert(bridge, @"A bridge instance is required to create an RCTRootView");
@@ -69,6 +70,7 @@ NSString *const RCTContentDidAppearNotification = @"RCTContentDidAppearNotificat
 
     _bridge = bridge;
     _moduleName = moduleName;
+    _initialProperties = [initialProperties copy];
     _loadingViewFadeDelay = 0.25;
     _loadingViewFadeDuration = 0.25;
 
@@ -81,7 +83,7 @@ NSString *const RCTContentDidAppearNotification = @"RCTContentDidAppearNotificat
                                              selector:@selector(hideLoadingView)
                                                  name:RCTContentDidAppearNotification
                                                object:self];
-    if (!_bridge.batchedBridge.isLoading) {
+    if (!_bridge.loading) {
       [self bundleFinishedLoading:_bridge.batchedBridge];
     }
 
@@ -92,13 +94,14 @@ NSString *const RCTContentDidAppearNotification = @"RCTContentDidAppearNotificat
 
 - (instancetype)initWithBundleURL:(NSURL *)bundleURL
                        moduleName:(NSString *)moduleName
+                initialProperties:(NSDictionary *)initialProperties
                     launchOptions:(NSDictionary *)launchOptions
 {
   RCTBridge *bridge = [[RCTBridge alloc] initWithBundleURL:bundleURL
                                             moduleProvider:nil
                                              launchOptions:launchOptions];
 
-  return [self initWithBridge:bridge moduleName:moduleName];
+  return [self initWithBridge:bridge moduleName:moduleName initialProperties:initialProperties];
 }
 
 RCT_NOT_IMPLEMENTED(-initWithFrame:(CGRect)frame)
@@ -158,30 +161,30 @@ RCT_NOT_IMPLEMENTED(-initWithCoder:(NSCoder *)aDecoder)
 - (void)javaScriptDidLoad:(NSNotification *)notification
 {
   RCTBridge *bridge = notification.userInfo[@"bridge"];
-  [self bundleFinishedLoading:bridge];
+  dispatch_async(dispatch_get_main_queue(), ^{
+    [self bundleFinishedLoading:bridge];
+  });
 }
 
 - (void)bundleFinishedLoading:(RCTBridge *)bridge
 {
-  dispatch_async(dispatch_get_main_queue(), ^{
+  if (!bridge.valid) {
-    if (!bridge.isValid) {
+    return;
-      return;
+  }
-    }
 
-    [_contentView removeFromSuperview];
+  [_contentView removeFromSuperview];
-    _contentView = [[RCTRootContentView alloc] initWithFrame:self.bounds bridge:bridge];
+  _contentView = [[RCTRootContentView alloc] initWithFrame:self.bounds bridge:bridge];
-    _contentView.backgroundColor = self.backgroundColor;
+  _contentView.backgroundColor = self.backgroundColor;
-    [self insertSubview:_contentView atIndex:0];
+  [self insertSubview:_contentView atIndex:0];
 
-    NSString *moduleName = _moduleName ?: @"";
+  NSString *moduleName = _moduleName ?: @"";
-    NSDictionary *appParameters = @{
+  NSDictionary *appParameters = @{
-      @"rootTag": _contentView.reactTag,
+    @"rootTag": _contentView.reactTag,
-      @"initialProps": _initialProperties ?: @{},
+    @"initialProps": _initialProperties ?: @{},
-    };
+  };
 
-    [bridge enqueueJSCall:@"AppRegistry.runApplication"
+  [bridge enqueueJSCall:@"AppRegistry.runApplication"
-                     args:@[moduleName, appParameters]];
+                   args:@[moduleName, appParameters]];
-  });
 }
 
 - (void)layoutSubviews