Add timing analytics for debugger page load (#3346)

Author: kenzieschmoll

packages/devtools_app/lib/src/analytics/_analytics_stub.dart

@@ -26,6 +26,14 @@ void screen(
   int value = 0,
 ]) {}
 
+void timeStart(String screenName, String timedOperation) {}
+
+void timeEnd(
+  String screenName,
+  String timedOperation, {
+  ScreenAnalyticsMetrics Function() screenMetricsProvider,
+}) {}
+
 void timeSync(
   String screenName,
   String timedOperation, {

packages/devtools_app/lib/src/analytics/_analytics_web.dart

@@ -275,6 +275,60 @@ void screen(
   );
 }
 
+String _operationKey(String screenName, String timedOperation) {
+  return '$screenName-$timedOperation';
+}
+
+final _timedOperationsInProgress = <String, DateTime>{};
+
+// Use this method coupled with `timeEnd` when an operation cannot be timed in
+// a callback, but rather needs to be timed instead at two disjoint start and
+// end marks.
+void timeStart(String screenName, String timedOperation) {
+  final startTime = DateTime.now();
+  final operationKey = _operationKey(
+    screenName,
+    timedOperation,
+  );
+  _timedOperationsInProgress[operationKey] = startTime;
+}
+
+// Use this method coupled with `timeStart` when an operation cannot be timed in
+// a callback, but rather needs to be timed instead at two disjoint start and
+// end marks.
+void timeEnd(
+  String screenName,
+  String timedOperation, {
+  ScreenAnalyticsMetrics Function() screenMetricsProvider,
+}) {
+  final endTime = DateTime.now();
+  final operationKey = _operationKey(
+    screenName,
+    timedOperation,
+  );
+  final startTime = _timedOperationsInProgress.remove(operationKey);
+  assert(startTime != null);
+  if (startTime == null) {
+    log(
+      'Could not time operation "$timedOperation" because a) `timeEnd` was '
+      'called before `timeStart` or b) the `screenName` and `timedOperation`'
+      'parameters for the `timeStart` and `timeEnd` calls do not match.',
+      LogLevel.warning,
+    );
+    return;
+  }
+  final durationMicros =
+      endTime.microsecondsSinceEpoch - startTime.microsecondsSinceEpoch;
+  _timing(
+    screenName,
+    timedOperation,
+    durationMicros: durationMicros,
+    screenMetrics:
+        screenMetricsProvider != null ? screenMetricsProvider() : null,
+  );
+}
+
+// Use this when a synchronous operation can be timed in a callback.
 void timeSync(
   String screenName,
   String timedOperation, {
@@ -305,6 +359,7 @@ void timeSync(
   );
 }
 
+// Use this when an asynchronous operation can be timed in a callback.
 Future<void> timeAsync(
   String screenName,
   String timedOperation, {

packages/devtools_app/lib/src/analytics/constants.dart

@@ -105,3 +105,6 @@ const String export = 'export';
 const String expandAll = 'expandAll';
 const String collapseAll = 'collapseAll';
 const String documentationLink = 'documentationLink';
+// This should track the time from `initState` for a screen to the time when
+// the page data has loaded and is ready to interact with.
+const String pageReady = 'pageReady';

packages/devtools_app/lib/src/debugger/debugger_screen.dart

@@ -9,6 +9,7 @@ import 'package:provider/provider.dart';
 import 'package:vm_service/vm_service.dart';
 
 import '../analytics/analytics.dart' as ga;
+import '../analytics/constants.dart' as analytics_constants;
 import '../auto_dispose_mixin.dart';
 import '../common_widgets.dart';
 import '../dialogs.dart';
@@ -80,10 +81,14 @@ class DebuggerScreenBodyState extends State<DebuggerScreenBody>
 
   DebuggerController controller;
 
+  bool _shownFirstScript;
+
   @override
   void initState() {
     super.initState();
     ga.screen(DebuggerScreen.id);
+    ga.timeStart(DebuggerScreen.id, analytics_constants.pageReady);
+    _shownFirstScript = false;
   }
 
   @override
@@ -95,11 +100,6 @@ class DebuggerScreenBodyState extends State<DebuggerScreenBody>
     controller = newController;
   }
 
-  @override
-  void dispose() {
-    super.dispose();
-  }
-
   void _onLocationSelected(ScriptLocation location) {
     if (location != null) {
       controller.showScriptLocation(location);
@@ -114,6 +114,13 @@ class DebuggerScreenBodyState extends State<DebuggerScreenBody>
         return ValueListenableBuilder(
           valueListenable: controller.currentParsedScript,
           builder: (context, parsedScript, _) {
+            if (scriptRef != null &&
+                parsedScript != null &&
+                !_shownFirstScript) {
+              ga.timeEnd(DebuggerScreen.id, analytics_constants.pageReady);
+              // TODO(annagrin): mark end of IPL timing for debugger page here.
+              _shownFirstScript = true;
+            }
             return CodeView(
               key: DebuggerScreenBody.codeViewKey,
               controller: controller,