changed Run behavior http://code.google.com/p/dart/issues/detail?id=2730,

editor/tools/plugins/com.google.dart.tools.debug.ui/src/com/google/dart/tools/debug/ui/launch/RunPropertyTester.java

Index: editor/tools/plugins/com.google.dart.tools.debug.ui/src/com/google/dart/tools/debug/ui/launch/RunPropertyTester.java
===================================================================
--- editor/tools/plugins/com.google.dart.tools.debug.ui/src/com/google/dart/tools/debug/ui/launch/RunPropertyTester.java	(revision 7163)
+++ editor/tools/plugins/com.google.dart.tools.debug.ui/src/com/google/dart/tools/debug/ui/launch/RunPropertyTester.java	(working copy)
@@ -16,7 +16,9 @@
 
 import com.google.dart.tools.core.DartCore;
 import com.google.dart.tools.core.internal.model.CompilationUnitImpl;
+import com.google.dart.tools.core.internal.model.DartLibraryImpl;
 import com.google.dart.tools.core.model.DartElement;
+import com.google.dart.tools.core.model.DartLibrary;
 
 import org.eclipse.core.expressions.PropertyTester;
 import org.eclipse.core.resources.IFile;
@@ -47,7 +49,13 @@
           DartElement element = DartCore.create((IFile) o);
           if (element instanceof CompilationUnitImpl
               && ((CompilationUnitImpl) element).definesLibrary()) {
-            return true;
+            DartLibrary library = ((CompilationUnitImpl) element).getLibrary();
+            if (library instanceof DartLibraryImpl) {
+              DartLibraryImpl impl = (DartLibraryImpl) library;
+              if (impl.isBrowserApplication() || impl.isServerApplication()) {
+                return true;
+              }
+            }
           }
         }
       }