[flutter_tools] fix debug stack traces (#50872)

dev/integration_tests/web/lib/stack_trace.dart

@@ -33,9 +33,9 @@ const List<StackFrame> expectedDebugStackFrames = <StackFrame>[
     number: -1,
     packageScheme: 'package',
     package: 'web_integration',
-    packagePath: 'stack_trace.dart.lib.js',
-    line: 138,
-    column: 15,
+    packagePath: 'stack_trace.dart',
+    line: 121,
+    column: 3,
     className: '<unknown>',
     method: 'baz',
     source: '',
@@ -44,9 +44,9 @@ const List<StackFrame> expectedDebugStackFrames = <StackFrame>[
     number: -1,
     packageScheme: 'package',
     package: 'web_integration',
-    packagePath: 'stack_trace.dart.lib.js',
-    line: 135,
-    column: 17,
+    packagePath: 'stack_trace.dart',
+    line: 116,
+    column: 3,
     className: '<unknown>',
     method: 'bar',
     source: '',
@@ -55,9 +55,9 @@ const List<StackFrame> expectedDebugStackFrames = <StackFrame>[
     number: -1,
     packageScheme: 'package',
     package: 'web_integration',
-    packagePath: 'stack_trace.dart.lib.js',
-    line: 132,
-    column: 17,
+    packagePath: 'stack_trace.dart',
+    line: 111,
+    column: 3,
     className: '<unknown>',
     method: 'foo',
     source: '',

packages/flutter_tools/lib/src/web/bootstrap.dart

@@ -194,7 +194,17 @@ define("main_module.bootstrap", ["$entrypoint", "dart_sdk"], function(app, dart_
       function(url) {
         url = url.replace(baseUrl, '/');
         var module = window.\$dartLoader.urlToModuleId.get(url);
-        if (!module) return null;
+        if (!module) {
+          if (url.endsWith('dart_sdk.js')) {
+            module = 'dart_sdk';
+          } else {
+            try {
+              module = '/packages' + url.split('packages')[1].split('.')[0] + '.dart';
+            } catch (e) {
+              return null;
+            }
+          }
+        }
         return dart.getSourceMap(module);
       });
   }