Support older SDKs in analyzer.

pkg/analyzer/lib/src/generated/sdk_io.dart

Index: pkg/analyzer/lib/src/generated/sdk_io.dart
diff --git a/pkg/analyzer/lib/src/generated/sdk_io.dart b/pkg/analyzer/lib/src/generated/sdk_io.dart
index d02d67ee8a7d85b4aa294cb3b342868b89e939fc..b155b9a784f0d0f9adde775b83fb4843bfb7c4f2 100644
--- a/pkg/analyzer/lib/src/generated/sdk_io.dart
+++ b/pkg/analyzer/lib/src/generated/sdk_io.dart
@@ -339,8 +339,10 @@ class DirectoryBasedDartSdk implements DartSdk {
   JavaFile get pubExecutable {
     if (_pubExecutable == null) {
       _pubExecutable = _verifyExecutable(new JavaFile.relative(
-          new JavaFile.relative(_sdkDirectory, _BIN_DIRECTORY_NAME), OSUtilities
-              .isWindows() ? _PUB_EXECUTABLE_NAME_WIN : _PUB_EXECUTABLE_NAME));
+          new JavaFile.relative(_sdkDirectory, _BIN_DIRECTORY_NAME),
+          OSUtilities.isWindows()
+              ? _PUB_EXECUTABLE_NAME_WIN
+              : _PUB_EXECUTABLE_NAME));
     }
     return _pubExecutable;
   }
@@ -397,6 +399,22 @@ class DirectoryBasedDartSdk implements DartSdk {
     return _vmExecutable;
   }
 
+  /**
+   * Determine the search order for trying to locate the [_LIBRARIES_FILE].
+   */
+  Iterable<JavaFile> get _libraryMapLocations sync* {
+    yield new JavaFile.relative(
+        new JavaFile.relative(
+            new JavaFile.relative(
+                new JavaFile.relative(libraryDirectory, _INTERNAL_DIR),
+                _SDK_LIBRARY_METADATA_DIR),
+            _SDK_LIBRARY_METADATA_LIB_DIR),
+        _LIBRARIES_FILE);
+    yield new JavaFile.relative(
+        new JavaFile.relative(libraryDirectory, _INTERNAL_DIR),
+        _LIBRARIES_FILE);
+  }
+
   @override
   Source fromFileUri(Uri uri) {
     JavaFile file = new JavaFile.fromUri(uri);
@@ -471,23 +489,24 @@ class DirectoryBasedDartSdk implements DartSdk {
    * is available. Return the initialized library map.
    */
   LibraryMap initialLibraryMap(bool useDart2jsPaths) {
-    JavaFile librariesFile = new JavaFile.relative(
-        new JavaFile.relative(
-          new JavaFile.relative(
-            new JavaFile.relative(libraryDirectory, _INTERNAL_DIR),
-            _SDK_LIBRARY_METADATA_DIR),
-          _SDK_LIBRARY_METADATA_LIB_DIR),
-        _LIBRARIES_FILE);
-    try {
-      String contents = librariesFile.readAsStringSync();
-      return new SdkLibrariesReader(useDart2jsPaths).readFromFile(
-          librariesFile, contents);
-    } catch (exception, stackTrace) {
-      AnalysisEngine.instance.logger.logError(
-          "Could not initialize the library map from ${librariesFile.getAbsolutePath()}",
-          new CaughtException(exception, stackTrace));
-      return new LibraryMap();
+    List<String> searchedPaths = <String>[];
+    var lastStackTrace = null;
+    var lastException = null;
+    for (JavaFile librariesFile in _libraryMapLocations) {
+      try {
+        String contents = librariesFile.readAsStringSync();
+        return new SdkLibrariesReader(useDart2jsPaths)
+            .readFromFile(librariesFile, contents);
+      } catch (exception, stackTrace) {
+        searchedPaths.add(librariesFile.getAbsolutePath());
+        lastException = exception;
+        lastStackTrace = stackTrace;
+      }
     }
+    AnalysisEngine.instance.logger.logError(
+        "Could not initialize the library map from $searchedPaths",
+        new CaughtException(lastException, lastStackTrace));
+    return new LibraryMap();
   }
 
   @override