Issue 3839. Warn when 'dart:io' and 'dart:html' are used in single library

editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/AnalysisMarkerManager.java

Index: editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/AnalysisMarkerManager.java
diff --git a/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/AnalysisMarkerManager.java b/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/AnalysisMarkerManager.java
index 4d2d74cd4709831b1637ead293ffae04324ea74a..b5a1a28ed7354b5068552d327b38c9028aede838 100644
--- a/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/AnalysisMarkerManager.java
+++ b/editor/tools/plugins/com.google.dart.tools.core/src/com/google/dart/tools/core/analysis/AnalysisMarkerManager.java
@@ -67,11 +67,12 @@ public class AnalysisMarkerManager implements AnalysisListener {
       }
 
       int severity;
+      ErrorSeverity errorSeverity = error.getErrorCode().getErrorSeverity();
       if (error.getErrorCode().getSubSystem() == SubSystem.STATIC_TYPE) {
         severity = IMarker.SEVERITY_WARNING;
-      } else if (error.getErrorCode().getErrorSeverity() == ErrorSeverity.ERROR) {
+      } else if (errorSeverity == ErrorSeverity.ERROR) {
         severity = IMarker.SEVERITY_ERROR;
-      } else if (error.getErrorCode().getErrorSeverity() == ErrorSeverity.WARNING) {
+      } else if (errorSeverity == ErrorSeverity.WARNING || errorSeverity == ErrorSeverity.INFO) {
         severity = IMarker.SEVERITY_WARNING;
       } else {
         return;