Fix for resolveRelativeUri() when the containedUri is absolute.

pkg/analyzer/test/generated/all_the_rest_test.dart

Index: pkg/analyzer/test/generated/all_the_rest_test.dart
diff --git a/pkg/analyzer/test/generated/all_the_rest_test.dart b/pkg/analyzer/test/generated/all_the_rest_test.dart
index 54cf5b00dcff21bf10c1cea634492045de1d140f..e7963a5b40b8f59d87d143433ae2259c2f0e2246 100644
--- a/pkg/analyzer/test/generated/all_the_rest_test.dart
+++ b/pkg/analyzer/test/generated/all_the_rest_test.dart
@@ -4164,6 +4164,13 @@ class ResolveRelativeUriTest {
     expect(relative.toString(), "dart:test/c/lib.dart");
   }
 
+  void test_resolveRelative_dart_dartUri() {
+    Uri uri = parseUriWithException('dart:foo');
+    Uri relative = resolveRelativeUri(uri, parseUriWithException('dart:bar'));
+    expect(relative, isNotNull);
+    expect(relative.toString(), 'dart:bar');
+  }
+
   void test_resolveRelative_dart_filePathWithParent() {
     Uri uri = parseUriWithException("dart:test/b/test.dart");
     Uri relative =
@@ -4186,6 +4193,13 @@ class ResolveRelativeUriTest {
     expect(relative.toString(), "package:lib.dart");
   }
 
+  void test_resolveRelative_package_dartUri() {
+    Uri uri = parseUriWithException('package:foo/bar.dart');
+    Uri relative = resolveRelativeUri(uri, parseUriWithException('dart:test'));
+    expect(relative, isNotNull);
+    expect(relative.toString(), 'dart:test');
+  }
+
   void test_resolveRelative_package_filePath() {
     Uri uri = parseUriWithException("package:b/test.dart");
     Uri relative = resolveRelativeUri(uri, parseUriWithException("c/lib.dart"));