First try to find the exact library for the given file URI.

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 b450bf6a00d938c1da06fc131bc979fcc3a06e61..f1f6b27acc4dfb248b517ea4e3ce2859662677a6 100644
--- a/pkg/analyzer/test/generated/all_the_rest_test.dart
+++ b/pkg/analyzer/test/generated/all_the_rest_test.dart
@@ -176,6 +176,18 @@ class DirectoryBasedDartSdkTest {
     expect(source.uri.toString(), "dart:core");
   }
 
+  void test_fromFile_library_firstExact() {
+    DirectoryBasedDartSdk sdk = _createDartSdk();
+    JavaFile dirHtml = new JavaFile.relative(sdk.libraryDirectory, "html");
+    JavaFile dirDartium = new JavaFile.relative(dirHtml, "dartium");
+    JavaFile file = new JavaFile.relative(dirDartium, "html_dartium.dart");
+    expect(file.isFile(), isTrue);
+    Source source = sdk.fromFileUri(file.toURI());
+    expect(source, isNotNull);
+    expect(source.isInSystemLibrary, isTrue);
+    expect(source.uri.toString(), "dart:html");
+  }
+
   void test_fromFile_part() {
     DirectoryBasedDartSdk sdk = _createDartSdk();
     Source source = sdk.fromFileUri(new JavaFile.relative(