Emulate compiling a source file in the context of an existing library. Add --debugger-compile flag …

pkg/dev_compiler/web/main.dart

Index: pkg/dev_compiler/web/main.dart
diff --git a/pkg/dev_compiler/web/main.dart b/pkg/dev_compiler/web/main.dart
index 3ec888884a9fbc71688d5bfb3e0b4d5ad9c6a210..70f84402fa591f260ad3291585f91f47830541ce 100755
--- a/pkg/dev_compiler/web/main.dart
+++ b/pkg/dev_compiler/web/main.dart
@@ -17,7 +17,7 @@ import 'web_command.dart';
 external set setUpCompilerInBrowser(Function function);
 
 Future main() async {
-  var args = ['compile'];
+  var args = ['compile', '--repl-compile'];
   _runCommand(args);
 }
 
@@ -61,7 +61,7 @@ int _handleError(dynamic error, dynamic stackTrace, List<String> args,
     messageHandler("We're sorry, you've found a bug in our compiler.");
     messageHandler("You can report this bug at:");
     messageHandler(
-      "    https://github.com/dart-lang/sdk/issues/labels/area-dev-compiler");
+        "    https://github.com/dart-lang/sdk/issues/labels/area-dev-compiler");
     messageHandler("");
     messageHandler(
         "Please include the information below in your report, along with");