Make Analyzer, VM and dart2js accept URI strings as part-of library identifier.

pkg/analyzer/test/src/dart/analysis/driver_test.dart

Index: pkg/analyzer/test/src/dart/analysis/driver_test.dart
diff --git a/pkg/analyzer/test/src/dart/analysis/driver_test.dart b/pkg/analyzer/test/src/dart/analysis/driver_test.dart
index 79e551fb2d420bb234117154b3c4e7f60f5d5fbd..53c4702f348ec0136b88e3e2509665a7c8433c9e 100644
--- a/pkg/analyzer/test/src/dart/analysis/driver_test.dart
+++ b/pkg/analyzer/test/src/dart/analysis/driver_test.dart
@@ -414,9 +414,14 @@ part of lib;
 
     AnalysisResult libResult = await driver.getResult(lib);
     List<AnalysisError> errors = libResult.errors;
-    expect(errors, hasLength(1));
-    expect(errors[0].errorCode,
-        ResolverErrorCode.MISSING_LIBRARY_DIRECTIVE_WITH_PART);
+    if (libResult.unit.element.context.analysisOptions.enableUriInPartOf) {
+      // TODO(28522): Should cause an error for wrong library name.
+      expect(errors, hasLength(0));
+    } else {
+        expect(errors, hasLength(1));
+        expect(errors[0].errorCode,
+            ResolverErrorCode.MISSING_LIBRARY_DIRECTIVE_WITH_PART);
+    }
   }
 
   test_analyze_resolveDirectives_error_partOfDifferentLibrary_byName() async {