Allow RCTRootView to be initialized with a frame

Summary:
If a root view is initialized with a bridge that is already loaded, then it immediately will initialize its content view with a zero size, which results in that content view's size being calculated according to its content instead of the size set on the root view after initialization. This would lead to a race condition where sometimes the content view has a smaller size than the root view.

Changelog:
[iOS][Added] - Allow RCTRootView to be initialized with a frame

Reviewed By: PeteTheHeat

Differential Revision: D27052637

fbshipit-source-id: 384ab3be27c92c0d84d34d49afb697882335d890

React/Base/RCTRootView.h

@@ -50,9 +50,18 @@ extern
 /**
  * - Designated initializer -
  */
+- (instancetype)initWithFrame:(CGRect)frame
+                       bridge:(RCTBridge *)bridge
+                   moduleName:(NSString *)moduleName
+            initialProperties:(nullable NSDictionary *)initialProperties NS_DESIGNATED_INITIALIZER;
+
+/**
+ * - Convenience initializer -
+ * The frame will default to CGRectZero.
+ */
 - (instancetype)initWithBridge:(RCTBridge *)bridge
                     moduleName:(NSString *)moduleName
-             initialProperties:(nullable NSDictionary *)initialProperties NS_DESIGNATED_INITIALIZER;
+             initialProperties:(nullable NSDictionary *)initialProperties;
 
 /**
  * - Convenience initializer -

React/Base/RCTRootView.m

@@ -44,9 +44,10 @@ NSString *const RCTContentDidAppearNotification = @"RCTContentDidAppearNotificat
   CGSize _intrinsicContentSize;
 }
 
-- (instancetype)initWithBridge:(RCTBridge *)bridge
-                    moduleName:(NSString *)moduleName
-             initialProperties:(NSDictionary *)initialProperties
+- (instancetype)initWithFrame:(CGRect)frame
+                       bridge:(RCTBridge *)bridge
+                   moduleName:(NSString *)moduleName
+            initialProperties:(NSDictionary *)initialProperties
 {
   RCTAssertMainQueue();
   RCTAssert(bridge, @"A bridge instance is required to create an RCTRootView");
@@ -57,7 +58,7 @@ NSString *const RCTContentDidAppearNotification = @"RCTContentDidAppearNotificat
     [bridge.performanceLogger markStartForTag:RCTPLTTI];
   }
 
-  if (self = [super initWithFrame:CGRectZero]) {
+  if (self = [super initWithFrame:frame]) {
     self.backgroundColor = [UIColor whiteColor];
 
     _bridge = bridge;
@@ -95,6 +96,13 @@ NSString *const RCTContentDidAppearNotification = @"RCTContentDidAppearNotificat
   return self;
 }
 
+- (instancetype)initWithBridge:(RCTBridge *)bridge
+                    moduleName:(NSString *)moduleName
+             initialProperties:(NSDictionary *)initialProperties
+{
+  return [self initWithFrame:CGRectZero bridge:bridge moduleName:moduleName initialProperties:initialProperties];
+}
+
 - (instancetype)initWithBundleURL:(NSURL *)bundleURL
                        moduleName:(NSString *)moduleName
                 initialProperties:(NSDictionary *)initialProperties