enable profiler for debug and profile modes

Author: Kaushik Iska

shell/platform/darwin/ios/framework/Source/FlutterEngine.mm

@@ -452,10 +452,19 @@ - (BOOL)createShell:(NSString*)entrypoint libraryURI:(NSString*)libraryURI {
   // initialized.
   fml::MessageLoop::EnsureInitializedForCurrentThread();
 
-  // TODO (kaushikiska): enable Profiler thread only in debug configurations.
+  flutter::ThreadHost::Type threadHostType = flutter::ThreadHost::Type::UI |
+                                             flutter::ThreadHost::Type::GPU |
+                                             flutter::ThreadHost::Type::IO;
+  bool profilerEnabled = false;
+#if (FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_DEBUG) || \
+    (FLUTTER_RUNTIME_MODE == FLUTTER_RUNTIME_MODE_PROFILE)
+  profilerEnabled = true;
+#endif
+  if (profilerEnabled) {
+    threadHostType = threadHostType | flutter::ThreadHost::Type::Profiler;
+  }
   _threadHost = {threadLabel.UTF8String,  // label
-                 flutter::ThreadHost::Type::UI | flutter::ThreadHost::Type::GPU |
-                     flutter::ThreadHost::Type::IO | flutter::ThreadHost::Type::Profiler};
+                 threadHostType};
 
   // Lambda captures by pointers to ObjC objects are fine here because the
   // create call is
@@ -471,7 +480,9 @@ - (BOOL)createShell:(NSString*)entrypoint libraryURI:(NSString*)libraryURI {
         return std::make_unique<flutter::Rasterizer>(shell, shell.GetTaskRunners());
       };
 
-  [self startProfiler];
+  if (profilerEnabled) {
+    [self startProfiler];
+  }
 
   if (flutter::IsIosEmbeddedViewsPreviewEnabled()) {
     // Embedded views requires the gpu and the platform views to be the same.