Use BufferContext + offset instead of BufferPointer.

pkg/analyzer/tool/summary/build_sdk_summaries.dart

 import 'dart:io';
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/java_io.dart';
 import 'package:analyzer/src/generated/sdk.dart';
 import 'package:analyzer/src/generated/sdk_io.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/summary/flat_buffers.dart' as fb;
@@ skipping 121 matching lines @@
   _BuilderOutput strong = new _Builder(sdkPath, true).build();
   return new _Output(spec, strong);
 }
 
 /**
  * Open the flat buffer in [inputPath] and extract the byte array in the [field]
  * into the [outputPath] file.
  */
 void _extractSingleOutput(String inputPath, int field, String outputPath) {
   List<int> bytes = new File(inputPath).readAsBytesSync();
-  fb.BufferPointer root = new fb.BufferPointer.fromBytes(bytes);
-  fb.BufferPointer table = root.derefObject();
-  List<int> fieldBytes = const fb.Uint8ListReader().vTableGet(table, field);
+  fb.BufferContext root = new fb.BufferContext.fromBytes(bytes);
+  int tableOffset = root.derefObject(0);
+  List<int> fieldBytes =
+      const fb.Uint8ListReader().vTableGet(root, tableOffset, field);
   new File(outputPath).writeAsBytesSync(fieldBytes, mode: FileMode.WRITE_ONLY);
 }
 
 /**
  * Print information about how to use the SDK summaries builder.
  */
 void _printUsage() {
 //  print('Usage: $BINARY_NAME command output_directory_path [sdk_path]');
   print('Usage: $BINARY_NAME command arguments');
   print('Where command can be one of the following:');
@@ skipping 108 matching lines @@
     }
   }
 }
 
 class _Output {
   final _BuilderOutput spec;
   final _BuilderOutput strong;
 
   _Output(this.spec, this.strong);
 }