-

packages/devtools_app/lib/src/screens/memory/framework/offline_data/offline_data.dart

@@ -46,10 +46,10 @@ class OfflineMemoryData {
   Map<String, dynamic> toJson() {
     return {
       _Json.selectedTab: selectedTab,
-      _Json.diffData: diff.toJson(),
-      _Json.profileData: profile.toJson(),
-      _Json.chartData: chart.toJson(),
-      _Json.classFilter: profile.classFilter.value.toJson(),
+      _Json.diffData: diff,
+      _Json.profileData: profile,
+      _Json.chartData: chart,
+      _Json.classFilter: profile.classFilter.value,
     };
   }
 }

packages/devtools_app/lib/src/screens/memory/panes/chart/controller/chart_data.dart

@@ -55,7 +55,7 @@ class ChartData {
   Map<String, dynamic> toJson() {
     return {
       _Json.isDeviceAndroid: isDeviceAndroid ?? false,
-      _Json.timeline: timeline.toJson(),
+      _Json.timeline: timeline,
       _Json.interval: displayInterval.name,
       _Json.isLegendVisible: isLegendVisible.value,
     };

packages/devtools_app/lib/src/screens/memory/panes/diff/controller/diff_pane_controller.dart

@@ -26,19 +26,50 @@ import '../data/csv.dart';
 import '../data/heap_diff_data.dart';
 import '../data/heap_diff_store.dart';
 import 'class_data.dart';
-import 'item_controller.dart';
+import 'snapshot_item.dart';
+
+class _Json {
+  static const snapshots = 'snapshots';
+  static const diffWith = 'diffWith';
+}
 
 class DiffPaneController extends DisposableController {
-  DiffPaneController({required this.loader});
+  DiffPaneController({
+    required this.loader,
+    List<SnapshotDataItem>? snapshots,
+  }) {
+    if (snapshots != null) {
+      core._snapshots.value.addAll(snapshots);
+    }
+    derived._updateValues();
+  }
 
   factory DiffPaneController.fromJson(Map<String, dynamic> json) {
-    // TODO(polina-c): implement, https://github.com/flutter/devtools/issues/6972
-    return DiffPaneController(loader: null);
+    final snapshots = (json[_Json.snapshots] as List)
+        .map((e) => SnapshotDataItem.fromJson(e))
+        .toList();
+    return DiffPaneController(
+      loader: null,
+      //snapshots: snapshots,
+    );
   }
 
   Map<String, dynamic> toJson() {
-    // TODO(polina-c): implement, https://github.com/flutter/devtools/issues/6972
-    return {};
+    final snapshots =
+        core.snapshots.value.whereType<SnapshotDataItem>().toList();
+
+    final snapshotToIndex =
+        snapshots.asMap().map((index, item) => MapEntry(item, index));
+
+    final diffsWith = snapshots.map((item) {
+      final diffWith = item.diffWith.value;
+      return diffWith == null ? null : snapshotToIndex[diffWith];
+    }).toList();
+
+    return {
+      _Json.snapshots: snapshots,
+      _Json.diffWith: diffsWith,
+    };
   }
 
   final HeapGraphLoader? loader;

packages/devtools_app/lib/src/screens/memory/panes/diff/controller/item_controller.dart → packages/devtools_app/lib/src/screens/memory/panes/diff/controller/snapshot_item.dart

@@ -33,6 +33,14 @@ class SnapshotDocItem extends SnapshotItem {
   bool get hasData => false;
 }
 
+class _Json {
+  static const defaultName = 'defaultName';
+  static const displayNumber = 'displayNumber';
+  static const snapshot = 'snapshot';
+  static const nameOverride = 'nameOverride';
+  static const diffWith = 'diffWith';
+}
+
 class SnapshotDataItem extends SnapshotItem implements RenamableItem {
   SnapshotDataItem({
     this.displayNumber,
@@ -41,6 +49,14 @@ class SnapshotDataItem extends SnapshotItem implements RenamableItem {
     _isProcessing.value = true;
   }
 
+  factory SnapshotDataItem.fromJson(Map<String, dynamic> json) {
+    throw UnimplementedError();
+  }
+
+  Map<String, dynamic> toJson() {
+    return {};
+  }
+
   HeapData? get heap => _heap;
   HeapData? _heap;
 

packages/devtools_app/lib/src/screens/memory/panes/diff/diff_pane.dart

@@ -15,7 +15,7 @@ import '../../../../shared/globals.dart';
 import '../../../../shared/primitives/simple_items.dart';
 import '../../shared/widgets/shared_memory_widgets.dart';
 import 'controller/diff_pane_controller.dart';
-import 'controller/item_controller.dart';
+import 'controller/snapshot_item.dart';
 import 'widgets/snapshot_control_pane.dart';
 import 'widgets/snapshot_list.dart';
 import 'widgets/snapshot_view.dart';
@@ -154,9 +154,9 @@ Find unexpected memory usage by comparing two heap snapshots:
 
 2. Use one of the following ways to get a **heap snapshot**:
 
-    a. To view current memory allocation click the ● button
+    a. To take snapshot of the connected application click the ● button
 
-    b. To import a snapshot taken with
+    b. To import a snapshot exported from DevTools or taken with
     [auto-snapshotting](https://github.com/dart-lang/leak_tracker/blob/main/doc/USAGE.md) or
     [writeHeapSnapshotToFile](https://api.flutter.dev/flutter/dart-developer/NativeRuntime/writeHeapSnapshotToFile.html)
     click the ![import]($uploadImageUrl) button

packages/devtools_app/lib/src/screens/memory/panes/diff/widgets/snapshot_control_pane.dart

@@ -12,7 +12,7 @@ import '../../../../../shared/memory/simple_items.dart';
 import '../../../../../shared/primitives/byte_utils.dart';
 import '../../../shared/primitives/simple_elements.dart';
 import '../controller/diff_pane_controller.dart';
-import '../controller/item_controller.dart';
+import '../controller/snapshot_item.dart';
 
 class SnapshotControlPane extends StatelessWidget {
   const SnapshotControlPane({super.key, required this.controller});

packages/devtools_app/lib/src/screens/memory/panes/diff/widgets/snapshot_list.dart

@@ -17,7 +17,7 @@ import '../../../../../shared/dialogs.dart';
 import '../../../../../shared/primitives/byte_utils.dart';
 import '../../../../../shared/primitives/utils.dart';
 import '../controller/diff_pane_controller.dart';
-import '../controller/item_controller.dart';
+import '../controller/snapshot_item.dart';
 
 final _log = Logger('snapshot_list');
 

packages/devtools_app/lib/src/screens/memory/panes/diff/widgets/snapshot_view.dart

@@ -9,7 +9,7 @@ import '../../../../../shared/common_widgets.dart';
 import '../../../../../shared/memory/classes.dart';
 import '../../../../../shared/primitives/utils.dart';
 import '../controller/diff_pane_controller.dart';
-import '../controller/item_controller.dart';
+import '../controller/snapshot_item.dart';
 import '../data/classes_diff.dart';
 import 'class_details/class_details.dart';
 import 'classes_table_diff.dart';

packages/devtools_app/lib/src/screens/memory/panes/profile/model.dart

@@ -83,11 +83,11 @@ class AdaptedProfile {
 
   Map<String, dynamic> toJson() {
     return {
-      _ProfileJson.total: _total.toJson(),
-      _ProfileJson.items: _items.map((e) => e.toJson()).toList(),
-      _ProfileJson.newGC: newSpaceGCStats.toJson(),
-      _ProfileJson.oldGC: oldSpaceGCStats.toJson(),
-      _ProfileJson.totalGC: totalGCStats.toJson(),
+      _ProfileJson.total: _total,
+      _ProfileJson.items: _items,
+      _ProfileJson.newGC: newSpaceGCStats,
+      _ProfileJson.oldGC: oldSpaceGCStats,
+      _ProfileJson.totalGC: totalGCStats,
     };
   }
 
@@ -221,7 +221,7 @@ class ProfileRecord with PinnableListEntry {
   Map<String, dynamic> toJson() {
     return {
       _RecordJson.isTotal: isTotal,
-      _RecordJson.heapClass: heapClass.toJson(),
+      _RecordJson.heapClass: heapClass,
       _RecordJson.totalInstances: totalInstances,
       _RecordJson.totalSize: totalSize,
       _RecordJson.totalDartHeapSize: totalDartHeapSize,

packages/devtools_app/lib/src/screens/memory/panes/profile/profile_pane_controller.dart

@@ -41,7 +41,7 @@ class ProfilePaneController extends DisposableController
 
   Map<String, dynamic> toJson() {
     return {
-      _jsonProfile: _currentAllocationProfile.value?.toJson(),
+      _jsonProfile: _currentAllocationProfile.value,
     };
   }
 

packages/devtools_app/lib/src/screens/memory/shared/primitives/memory_timeline.dart

@@ -26,7 +26,7 @@ class MemoryTimeline {
 
   Map<String, dynamic> toJson() {
     return {
-      _jsonData: data.map((e) => e.toJson()).toList(),
+      _jsonData: data,
     };
   }
 

packages/devtools_app/test/memory/diff/widgets/class_filter_test.dart

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'package:devtools_app/src/screens/memory/panes/diff/controller/item_controller.dart';
+import 'package:devtools_app/src/screens/memory/panes/diff/controller/snapshot_item.dart';
 import 'package:devtools_app/src/screens/memory/panes/diff/diff_pane.dart';
 import 'package:devtools_app/src/screens/memory/shared/heap/class_filter.dart';
 import 'package:devtools_app/src/screens/memory/shared/widgets/class_filter.dart';

packages/devtools_shared/lib/src/memory/event_sample.dart

@@ -129,14 +129,6 @@ class ExtensionEvents {
     return ExtensionEvents(events);
   }
 
-  final theEvents = <ExtensionEvent>[];
-
-  bool get isEmpty => theEvents.isEmpty;
-
-  bool get isNotEmpty => theEvents.isNotEmpty;
-
-  void clear() => theEvents.clear();
-
   Map<String, dynamic> toJson() {
     final eventsAsJson = <String, dynamic>{};
     var index = 0;
@@ -148,6 +140,14 @@ class ExtensionEvents {
     return eventsAsJson;
   }
 
+  final theEvents = <ExtensionEvent>[];
+
+  bool get isEmpty => theEvents.isEmpty;
+
+  bool get isNotEmpty => theEvents.isNotEmpty;
+
+  void clear() => theEvents.clear();
+
   @override
   String toString() => '[ExtensionEvents = '
       '${const JsonEncoder.withIndent('  ').convert(toJson())}]';

packages/devtools_shared/lib/src/memory/heap_sample.dart

@@ -53,9 +53,9 @@ class HeapSample {
         'used': used,
         'external': external,
         'gc': isGC,
-        'adb_memoryInfo': adbMemoryInfo.toJson(),
-        'memory_eventInfo': memoryEventInfo.toJson(),
-        'raster_cache': rasterCache.toJson(),
+        'adb_memoryInfo': adbMemoryInfo,
+        'memory_eventInfo': memoryEventInfo,
+        'raster_cache': rasterCache,
       };
 
   /// Version of HeapSample JSON payload.