Make executeAsyncBlockOnJavaScriptQueue required

Summary: This leaves no optional methods on `RCTJavaScriptExecutor`, which is certainly a good thing.

Reviewed By: majak

Differential Revision: D3518915

fbshipit-source-id: e606b9076c3299f81a225a181ea244148a1832cb

React/Base/RCTBatchedBridge.m

@@ -747,18 +747,11 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
 - (void)_immediatelyCallTimer:(NSNumber *)timer
 {
   RCTAssertJSThread();
-
-  dispatch_block_t block = ^{
+  [_javaScriptExecutor executeAsyncBlockOnJavaScriptQueue:^{
     [self _actuallyInvokeAndProcessModule:@"JSTimersExecution"
                                    method:@"callTimers"
                                 arguments:@[@[timer]]];
-  };
-
-  if ([_javaScriptExecutor respondsToSelector:@selector(executeAsyncBlockOnJavaScriptQueue:)]) {
-    [_javaScriptExecutor executeAsyncBlockOnJavaScriptQueue:block];
-  } else {
-    [_javaScriptExecutor executeBlockOnJavaScriptQueue:block];
-  }
+  }];
 }
 
 - (void)enqueueApplicationScript:(NSData *)script

React/Base/RCTJavaScriptExecutor.h

@@ -76,8 +76,6 @@ typedef void (^RCTJavaScriptCallback)(id json, NSError *error);
  */
 - (void)executeBlockOnJavaScriptQueue:(dispatch_block_t)block;
 
-@optional
-
 /**
  * Special case for Timers + ContextExecutor - instead of the default
  *   if jsthread then call else dispatch call on jsthread