Update semantic highlighting only if there are no parse errors

editor/tools/plugins/com.google.dart.tools.ui/src/com/google/dart/tools/ui/internal/text/editor/SemanticHighlightingReconciler.java

Index: editor/tools/plugins/com.google.dart.tools.ui/src/com/google/dart/tools/ui/internal/text/editor/SemanticHighlightingReconciler.java
diff --git a/editor/tools/plugins/com.google.dart.tools.ui/src/com/google/dart/tools/ui/internal/text/editor/SemanticHighlightingReconciler.java b/editor/tools/plugins/com.google.dart.tools.ui/src/com/google/dart/tools/ui/internal/text/editor/SemanticHighlightingReconciler.java
index c804c7712461ae7b6d887d25240a826bdbef36ef..6cd93873b4dc19a30224c695c652ba8fe32bab39 100644
--- a/editor/tools/plugins/com.google.dart.tools.ui/src/com/google/dart/tools/ui/internal/text/editor/SemanticHighlightingReconciler.java
+++ b/editor/tools/plugins/com.google.dart.tools.ui/src/com/google/dart/tools/ui/internal/text/editor/SemanticHighlightingReconciler.java
@@ -303,6 +303,11 @@ public class SemanticHighlightingReconciler implements IDartReconcilingListener,
 
   @Override
   public void reconciled(DartUnit ast, boolean forced, IProgressMonitor progressMonitor) {
+    // don't update semantic highlighting if there are parsing problems to avoid "flashing"
+    if (ast.hasParseErrors()) {
+      return;
+    }
+
     // ensure at most one thread can be reconciling at any time
     synchronized (fReconcileLock) {
       if (fIsReconciling) {