Log bridge description for e2e reloads

Reviewed By: mhorowitz

Differential Revision: D7577953

fbshipit-source-id: 96871c664cb7ec84570bc76f2edb36ff8c8c6aeb

React/Base/RCTBridge.h

@@ -72,6 +72,12 @@ RCT_EXTERN NSString *const RCTBridgeDidDownloadScriptNotification;
  */
 RCT_EXTERN NSString *const RCTBridgeDidDownloadScriptNotificationSourceKey;
 
+/**
+ * Key for the bridge description (NSString_ in the
+ * RCTBridgeDidDownloadScriptNotification userInfo dictionary.
+ */
+RCT_EXTERN NSString *const RCTBridgeDidDownloadScriptNotificationBridgeDescriptionKey;
+
 /**
  * This block can be used to instantiate modules that require additional
  * init parameters, or additional configuration prior to being used.

React/Base/RCTBridge.m

@@ -31,6 +31,7 @@ NSString *const RCTBridgeWillReloadNotification = @"RCTBridgeWillReloadNotificat
 NSString *const RCTBridgeWillDownloadScriptNotification = @"RCTBridgeWillDownloadScriptNotification";
 NSString *const RCTBridgeDidDownloadScriptNotification = @"RCTBridgeDidDownloadScriptNotification";
 NSString *const RCTBridgeDidDownloadScriptNotificationSourceKey = @"source";
+NSString *const RCTBridgeDidDownloadScriptNotificationBridgeDescriptionKey = @"bridgeDescription";
 
 static NSMutableArray<Class> *RCTModuleClasses;
 NSArray<Class> *RCTGetModuleClasses(void)

React/CxxBridge/RCTCxxBridge.mm

@@ -400,7 +400,11 @@ struct RCTInstanceCallback : public InstanceCallback {
     [performanceLogger markStopForTag:RCTPLScriptDownload];
     [performanceLogger setValue:source.length forTag:RCTPLBundleSize];
 
-    NSDictionary *userInfo = source ? @{ RCTBridgeDidDownloadScriptNotificationSourceKey: source } : nil;
+    NSDictionary *userInfo = @{
+      RCTBridgeDidDownloadScriptNotificationSourceKey: source ?: [NSNull null],
+      RCTBridgeDidDownloadScriptNotificationBridgeDescriptionKey: self->_bridgeDescription ?: [NSNull null],
+    };
+
     [center postNotificationName:RCTBridgeDidDownloadScriptNotification object:self->_parentBridge userInfo:userInfo];
 
     _onSourceLoad(error, source);