Allow profile widget builds in profile mode (#30990)

## Description

Previously, such function is only available in the debug mode. But the
performance information is very noisy in debug mode with JIT. I feel
that such function is as important and useful as the performance overlay
and the `--trace-skia` option for the GPU thread.  So we should give it
the same ability to run in both profile and debug mode.

I've tested it using flutter_gallery in the profile mode. There's no
observable difference in the performance overlay between toggling widget
build profiling.

## Related Issues

https://github.com/flutter/flutter/issues/30984

packages/flutter/lib/src/widgets/binding.dart

@@ -302,6 +302,16 @@ mixin WidgetsBinding on BindingBase, SchedulerBinding, GestureBinding, RendererB
           };
         },
       );
+
+      // Expose the ability to send Widget rebuilds as [Timeline] events.
+      registerBoolServiceExtension(
+        name: 'profileWidgetBuilds',
+        getter: () async => debugProfileBuildsEnabled,
+        setter: (bool value) async {
+          if (debugProfileBuildsEnabled != value)
+            debugProfileBuildsEnabled = value;
+        },
+      );
     }
 
     assert(() {
@@ -316,16 +326,6 @@ mixin WidgetsBinding on BindingBase, SchedulerBinding, GestureBinding, RendererB
         },
       );
 
-      // Expose the ability to send Widget rebuilds as [Timeline] events.
-      registerBoolServiceExtension(
-        name: 'profileWidgetBuilds',
-        getter: () async => debugProfileBuildsEnabled,
-        setter: (bool value) async {
-          if (debugProfileBuildsEnabled != value)
-            debugProfileBuildsEnabled = value;
-        },
-      );
-
       // This service extension is deprecated and will be removed by 12/1/2018.
       // Use ext.flutter.inspector.show instead.
       registerBoolServiceExtension(

packages/flutter/lib/src/widgets/framework.dart

@@ -3730,11 +3730,8 @@ abstract class ComponentElement extends Element {
   /// [rebuild] when the element needs updating.
   @override
   void performRebuild() {
-    assert(() {
-      if (debugProfileBuildsEnabled)
-        Timeline.startSync('${widget.runtimeType}',  arguments: timelineWhitelistArguments);
-      return true;
-    }());
+    if (!kReleaseMode && debugProfileBuildsEnabled)
+      Timeline.startSync('${widget.runtimeType}',  arguments: timelineWhitelistArguments);
 
     assert(_debugSetAllowIgnoredCallsToMarkNeedsBuild(true));
     Widget built;
@@ -3757,11 +3754,8 @@ abstract class ComponentElement extends Element {
       _child = updateChild(null, built, slot);
     }
 
-    assert(() {
-      if (debugProfileBuildsEnabled)
-        Timeline.finishSync();
-      return true;
-    }());
+    if (!kReleaseMode && debugProfileBuildsEnabled)
+      Timeline.finishSync();
   }
 
   /// Subclasses should override this function to actually call the appropriate

packages/flutter_tools/lib/src/resident_runner.dart

@@ -884,7 +884,7 @@ abstract class ResidentRunner {
       }
       return true;
     } else if (character == 'a') {
-      if (supportsServiceProtocol && isRunningDebug) {
+      if (supportsServiceProtocol) {
         await _debugToggleProfileWidgetBuilds();
       }
     } else if (lower == 'o') {
@@ -993,12 +993,12 @@ abstract class ResidentRunner {
         printStatus('To toggle the widget inspector (WidgetsApp.showWidgetInspectorOverride), press "i".');
         printStatus('To toggle the display of construction lines (debugPaintSizeEnabled), press "p".');
         printStatus('To simulate different operating systems, (defaultTargetPlatform), press "o".');
-        printStatus('To enable timeline events for all widget build methods, (debugProfileWidgetBuilds), press "a"');
         printStatus('To toggle the elevation checker, press "z".');
       } else {
         printStatus('To dump the accessibility tree (debugDumpSemantics), press "S" (for traversal order) or "U" (for inverse hit test order).');
       }
       printStatus('To display the performance overlay (WidgetsApp.showPerformanceOverlay), press "P".');
+      printStatus('To enable timeline events for all widget build methods, (debugProfileWidgetBuilds), press "a"');
     }
     if (flutterDevices.any((FlutterDevice d) => d.device.supportsScreenshot)) {
       printStatus('To save a screenshot to flutter.png, press "s".');