Bump up the buffer size and show a warning if the trace might be truncated

Summary: The current buffer size isn't enough even to capture a short TTI trace.

Reviewed By: mhorowitz

Differential Revision: D10112538

fbshipit-source-id: 266fa6ffa916049245b21d7725a364d75589c776

React/CxxBridge/RCTCxxBridge.mm

@@ -1261,6 +1261,10 @@ RCT_NOT_IMPLEMENTED(- (instancetype)initWithBundleURL:(__unused NSURL *)bundleUR
       NSData *logData = [log dataUsingEncoding:NSUTF8StringEncoding];
       callback(logData);
       #if WITH_FBSYSTRACE
+      if (![RCTFBSystrace verifyTraceSize:logData.length]) {
+        RCTLogWarn(@"Your FBSystrace trace might be truncated, try to bump up the buffer size"
+                   " in RCTFBSystrace.m or capture a shorter trace");
+      }
       [RCTFBSystrace unregisterCallbacks];
       #endif
     });