Use a slightly faster way to write index data.

pkg/analysis_server/lib/src/services/index/store/split_store.dart

Index: pkg/analysis_server/lib/src/services/index/store/split_store.dart
diff --git a/pkg/analysis_server/lib/src/services/index/store/split_store.dart b/pkg/analysis_server/lib/src/services/index/store/split_store.dart
index fc1ca31616d9a87571296627fddb1db75f9af3d2..7e65c174d0d5d389e738d98320d9ac51bf3aad4c 100644
--- a/pkg/analysis_server/lib/src/services/index/store/split_store.dart
+++ b/pkg/analysis_server/lib/src/services/index/store/split_store.dart
@@ -6,7 +6,6 @@ library services.src.index.store.split_store;
 
 import 'dart:async';
 import 'dart:collection';
-import 'dart:io';
 import 'dart:typed_data';
 
 import 'package:analysis_server/src/services/index/index.dart';
@@ -988,7 +987,7 @@ class _DataInputStream {
   }
 
   int readInt() {
-    int result = _byteData.getInt32(_byteOffset);
+    int result = _byteData.getInt32(_byteOffset, Endianness.HOST_ENDIAN);
     _byteOffset += 4;
     return result;
   }
@@ -996,16 +995,23 @@ class _DataInputStream {
 
 
 class _DataOutputStream {
-  BytesBuilder _buffer = new BytesBuilder();
+  static const LIST_SIZE = 1024;
+  int _size = LIST_SIZE;
+  Uint32List _buf = new Uint32List(LIST_SIZE);
+  int _pos = 0;
 
   Uint8List getBytes() {
-    return new Uint8List.fromList(_buffer.takeBytes());
+    return new Uint8List.view(_buf.buffer, 0, _size << 2);
   }
 
   void writeInt(int value) {
-    _buffer.addByte((value & 0xFF000000) >> 24);
-    _buffer.addByte((value & 0x00FF0000) >> 16);
-    _buffer.addByte((value & 0x0000FF00) >> 8);
-    _buffer.addByte(value & 0xFF);
+    if (_pos == _size) {
+      int newSize = _size << 1;
+      Uint32List newBuf = new Uint32List(newSize);
+      newBuf.setRange(0, _size, _buf);
+      _size = newSize;
+      _buf = newBuf;
+    }
+    _buf[_pos++] = value;
   }
 }