Don't allow download percentage to exceed expectations

Summary:
This diff updates the loading banner to protect against showing percentages over 100%

Changelog: [Fixed] [iOS] Cap loading bar percentage at 100%

Reviewed By: shergin

Differential Revision: D21295809

fbshipit-source-id: 343f53acafa126800367444562730eff4ae67af4

React/Base/RCTJavaScriptLoader.mm

@@ -52,7 +52,9 @@ - (NSString *)description
   NSMutableString *desc = [NSMutableString new];
   [desc appendString:_status ?: @"Bundling"];
 
-  if ([_total integerValue] > 0) {
+  if ([_total integerValue] > 0 && [_done integerValue] > [_total integerValue]) {
+    [desc appendFormat:@" %ld%%", (long)100];
+  } else if ([_total integerValue] > 0) {
     [desc appendFormat:@" %ld%%", (long)(100 * [_done integerValue] / [_total integerValue])];
   } else {
     [desc appendFormat:@" %ld%%", (long)0];