Remove usage of std::string in EarlyJsErrorHandler

Summary:
This would fix test errors caused by including <string> in non-C++ compatible files.

Changelog:
[General][Changed] - Remove usage of std::string in EarlyJsErrorHandler.

Reviewed By: RSNara

Differential Revision: D35645334

fbshipit-source-id: 7f04d2c66d53dc1eef63367de1a64ed9273898f5

React/CoreModules/RCTExceptionsManager.h

@@ -7,7 +7,6 @@
 
 #import <Foundation/Foundation.h>
 #import <React/RCTBridgeModule.h>
-#import <string>
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -39,7 +38,7 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)reportFatalException:(nullable NSString *)message
                        stack:(nullable NSArray<NSDictionary *> *)stack
                  exceptionId:(double)exceptionId;
-- (void)reportEarlyJsException:(std::string)errorMap;
+- (void)reportEarlyJsException:(NSString *)errorMap;
 
 @property (nonatomic, weak) id<RCTExceptionsManagerDelegate> delegate;
 

React/CoreModules/RCTExceptionsManager.mm

@@ -150,10 +150,9 @@ - (void)reportFatal:(NSString *)message
   }
 }
 
-- (void)reportEarlyJsException:(std::string)errorMap
+- (void)reportEarlyJsException:(NSString *)errorStr
 {
-  NSString *errprStr = [NSString stringWithUTF8String:errorMap.c_str()];
-  NSData *jsonData = [errprStr dataUsingEncoding:NSUTF8StringEncoding];
+  NSData *jsonData = [errorStr dataUsingEncoding:NSUTF8StringEncoding];
   NSError *jsonError;
   NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:jsonData
                                                        options:NSJSONWritingPrettyPrinted