Emit classes using ASTs

sdk/lib/_internal/compiler/implementation/code_buffer.dart

Index: sdk/lib/_internal/compiler/implementation/code_buffer.dart
diff --git a/sdk/lib/_internal/compiler/implementation/code_buffer.dart b/sdk/lib/_internal/compiler/implementation/code_buffer.dart
index 023db92c05c52105ab3e3b35a6fd52d4cdc487c5..b3b48525677f24c10eabbeb353f3d15ce944678d 100644
--- a/sdk/lib/_internal/compiler/implementation/code_buffer.dart
+++ b/sdk/lib/_internal/compiler/implementation/code_buffer.dart
@@ -45,7 +45,7 @@ class CodeBuffer implements StringBuffer {
       }
       lastBufferOffset = buffer.length + other.lastBufferOffset;
     }
-    buffer.add(other.toString());
+    buffer.add(other.getText());
   }
 
   CodeBuffer addAll(Collection<Object> objects) {
@@ -67,6 +67,10 @@ class CodeBuffer implements StringBuffer {
   }
 
   String toString() {
+    throw "Don't use CodeBuffer.toString() since it drops sourcemap data.";
+  }
+
+  String getText() {
     return buffer.toString();
   }