Implement new constant expressions

editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/constant/ConstantEvaluatorTest.java

Index: editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/constant/ConstantEvaluatorTest.java
diff --git a/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/constant/ConstantEvaluatorTest.java b/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/constant/ConstantEvaluatorTest.java
index 3aaf9246e62eeaffebc04550f314a240998a07b1..3c93491fb1b396113f4cfd1e6b2ea231cb90a048 100644
--- a/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/constant/ConstantEvaluatorTest.java
+++ b/editor/tools/plugins/com.google.dart.engine_test/src/com/google/dart/engine/constant/ConstantEvaluatorTest.java
@@ -313,6 +313,10 @@ public class ConstantEvaluatorTest extends ResolverTestCase {
     assertValue(5L, "2 + 3");
   }
 
+  public void test_plus_string_string() throws Exception {
+    assertValue("ab", "'a' + 'b'");
+  }
+
   public void test_remainder_double_double() throws Exception {
     assertValue(3.2 % 2.3, "3.2 % 2.3");
   }
@@ -325,6 +329,14 @@ public class ConstantEvaluatorTest extends ResolverTestCase {
     assertValue(16L, "64 >> 2");
   }
 
+  public void test_stringLength_complex() throws Exception {
+    assertValue(6L, "('qwe' + 'rty').length");
+  }
+
+  public void test_stringLength_simple() throws Exception {
+    assertValue(6L, "'Dvorak'.length");
+  }
+
   public void test_times_double_double() throws Exception {
     assertValue(2.3 * 3.2, "2.3 * 3.2");
   }