[ddc] Fix sourcemap on debugger statements

Add test file exercising the lack of distinct sourcemaps.

Change-Id: I35e099b2a91d5b6516adaa3cb034ab0b84262fed
Fixes: https://github.com/dart-lang/sdk/issues/45544
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/194019
Reviewed-by: Mark Zhou <markzipan@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Commit-Queue: Nicholas Shahan <nshahan@google.com>

pkg/dev_compiler/lib/src/kernel/compiler.dart

@@ -5294,8 +5294,9 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
       // Inline `debugger()` with no arguments, as a statement if possible,
       // otherwise as an immediately invoked function.
       return isStatement
-          ? js.statement('debugger;')
-          : js.call('(() => { debugger; return true})()');
+          ? js_ast.DebuggerStatement()
+          : js.call(
+              '(() => { #; return true})()', [js_ast.DebuggerStatement()]);
     }
 
     // The signature of `debugger()` is:

pkg/dev_compiler/test/sourcemap/testfiles/multiple_debugger_calls.dart

@@ -0,0 +1,24 @@
+// Copyright (c) 2021, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// @dart = 2.9
+
+import 'dart:developer';
+
+void main() {
+  print('1');
+  /*sl:1*/ debugger();
+  print('2');
+  /*sl:2*/ debugger();
+  print('3');
+  foo(/*s:3*/ debugger());
+  print('4');
+  /*sl:4*/ debugger();
+  print('5');
+  foo(/*s:5*/ debugger());
+  print('6');
+  foo(/*s:6*/ debugger());
+}
+
+void foo(bool _) => null;