avoid incorrect usage of TimelineTask (#127527)

This code was added based on a misunderstanding of the API surface.

dev/tracing_tests/test/image_cache_tracing_test.dart

@@ -34,11 +34,18 @@ void main() {
       <Map<String, dynamic>>[
         <String, dynamic>{
           'name': 'ImageCache.putIfAbsent',
-          'args': <String, dynamic>{'key': 'Test', 'isolateId': isolateId},
+          'args': <String, dynamic>{
+            'key': 'Test',
+            'isolateId': isolateId,
+            'parentId': null,
+          },
         },
         <String, dynamic>{
           'name': 'listener',
-          'args': <String, dynamic>{'isolateId': isolateId},
+          'args': <String, dynamic>{
+            'isolateId': isolateId,
+            'parentId': null,
+          },
         },
         <String, dynamic>{
           'name': 'ImageCache.clear',
@@ -48,15 +55,24 @@ void main() {
             'liveImages': 1,
             'currentSizeInBytes': 0,
             'isolateId': isolateId,
+            'parentId': null,
           },
         },
         <String, dynamic>{
           'name': 'ImageCache.putIfAbsent',
-          'args': <String, dynamic>{'key': 'Test2', 'isolateId': isolateId},
+          'args': <String, dynamic>{
+            'key': 'Test2',
+            'isolateId': isolateId,
+            'parentId': null,
+          },
         },
         <String, dynamic>{
           'name': 'ImageCache.evict',
-          'args': <String, dynamic>{'sizeInBytes': 4, 'isolateId': isolateId},
+          'args': <String, dynamic>{
+            'sizeInBytes': 4,
+            'isolateId': isolateId,
+            'parentId': null,
+          },
         },
       ],
     );

packages/flutter/lib/src/painting/image_cache.dart

@@ -325,7 +325,6 @@ class ImageCache {
   /// cause other images in the cache to be evicted.
   ImageStreamCompleter? putIfAbsent(Object key, ImageStreamCompleter Function() loader, { ImageErrorListener? onError }) {
     TimelineTask? timelineTask;
-    TimelineTask? listenerTask;
     if (!kReleaseMode) {
       timelineTask = TimelineTask()..start(
         'ImageCache.putIfAbsent',
@@ -398,7 +397,7 @@ class ImageCache {
     }
 
     if (!kReleaseMode) {
-      listenerTask = TimelineTask(parent: timelineTask)..start('listener');
+      timelineTask!.start('listener');
     }
     // A multi-frame provider may call the listener more than once. We need do make
     // sure that some cleanup works won't run multiple times, such as finishing the
@@ -425,7 +424,7 @@ class ImageCache {
 
       // Only touch if the cache was enabled when resolve was initially called.
       if (trackPendingImage) {
-        _touch(key, image, listenerTask);
+        _touch(key, image, timelineTask);
       } else {
         image.dispose();
       }
@@ -435,14 +434,15 @@ class ImageCache {
         pendingImage.removeListener();
       }
       if (!kReleaseMode && !listenedOnce) {
-        listenerTask!.finish(arguments: <String, dynamic>{
-          'syncCall': syncCall,
-          'sizeInBytes': sizeBytes,
-        });
-        timelineTask!.finish(arguments: <String, dynamic>{
-          'currentSizeBytes': currentSizeBytes,
-          'currentSize': currentSize,
-        });
+        timelineTask!
+          ..finish(arguments: <String, dynamic>{
+            'syncCall': syncCall,
+            'sizeInBytes': sizeBytes,
+          })
+          ..finish(arguments: <String, dynamic>{
+            'currentSizeBytes': currentSizeBytes,
+            'currentSize': currentSize,
+          });
       }
       listenedOnce = true;
     }
@@ -504,9 +504,8 @@ class ImageCache {
   // maximum, or the cache is empty.
   void _checkCacheSize(TimelineTask? timelineTask) {
     final Map<String, dynamic> finishArgs = <String, dynamic>{};
-    TimelineTask? checkCacheTask;
     if (!kReleaseMode) {
-      checkCacheTask = TimelineTask(parent: timelineTask)..start('checkCacheSize');
+      timelineTask!.start('checkCacheSize');
       finishArgs['evictedKeys'] = <String>[];
       finishArgs['currentSize'] = currentSize;
       finishArgs['currentSizeBytes'] = currentSizeBytes;
@@ -524,7 +523,7 @@ class ImageCache {
     if (!kReleaseMode) {
       finishArgs['endSize'] = currentSize;
       finishArgs['endSizeBytes'] = currentSizeBytes;
-      checkCacheTask!.finish(arguments: finishArgs);
+      timelineTask!.finish(arguments: finishArgs);
     }
     assert(_currentSizeBytes >= 0);
     assert(_cache.length <= maximumSize);