Use specialized _FbUint8List and Uint8ListReader.

pkg/analyzer/tool/summary/build_sdk_summaries.dart

Index: pkg/analyzer/tool/summary/build_sdk_summaries.dart
diff --git a/pkg/analyzer/tool/summary/build_sdk_summaries.dart b/pkg/analyzer/tool/summary/build_sdk_summaries.dart
index 6cd5fb5f14227e333055e9e0173f463502aead0a..4f5db1e27b872b55aab3564a0c50aa494ef92415 100644
--- a/pkg/analyzer/tool/summary/build_sdk_summaries.dart
+++ b/pkg/analyzer/tool/summary/build_sdk_summaries.dart
@@ -133,10 +133,9 @@ _Output _buildMultipleOutputs(String sdkPath) {
  */
 void _extractSingleOutput(String inputPath, int field, String outputPath) {
   List<int> bytes = new File(inputPath).readAsBytesSync();
-  fb.BufferPointer bp = new fb.BufferPointer.fromBytes(bytes);
-  fb.BufferPointer table = bp.derefObject();
-  List<int> fieldBytes =
-      const fb.ListReader(const fb.Uint8Reader()).vTableGet(table, field);
+  fb.BufferPointer root = new fb.BufferPointer.fromBytes(bytes);
+  fb.BufferPointer table = root.derefObject();
+  List<int> fieldBytes = const fb.Uint8ListReader().vTableGet(table, field);
   new File(outputPath).writeAsBytesSync(fieldBytes, mode: FileMode.WRITE_ONLY);
 }