Issue 5293. Invocation of an undefined static method should be a warning, not an error

compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java

Index: compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java
diff --git a/compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java b/compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java
index 7e421896ecfed109cd322c844fa4173578e65a75..ed9c8115841115b1ef2b13c00e605e43d2318ab6 100644
--- a/compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java
+++ b/compiler/java/com/google/dart/compiler/resolver/ResolverErrorCode.java
@@ -138,8 +138,8 @@ public enum ResolverErrorCode implements ErrorCode {
   INVALID_TYPE_NAME_IN_CONSTRUCTOR("Invalid type in constructor name"),
   // TODO(zundel): error message needs JUnit test (reachable code?)
   IS_A_CONSTRUCTOR("%s.%s is a constructor, expected a  method"),
-  IS_AN_INSTANCE_FIELD("%s.%s is an instance field, not a static method"),
-  IS_AN_INSTANCE_METHOD("%s.%s is an instance method, not a static method"),
+  IS_AN_INSTANCE_FIELD(ErrorSeverity.WARNING, "%s.%s is an instance field, not a static method"),
+  IS_AN_INSTANCE_METHOD(ErrorSeverity.WARNING, "%s.%s is an instance method, not a static method"),
   // TODO(zundel): error message needs JUnit test (requires development mode checks)
   LIST_LITERAL_ELEMENT_TYPE(
       "List literal element type must match declaration '%s' when type checks are on."),