fasta: Use more efficient Uint16List/Uint32List for line offset information, use hints for length

pkg/front_end/lib/src/fasta/scanner/utf8_bytes_scanner.dart

Index: pkg/front_end/lib/src/fasta/scanner/utf8_bytes_scanner.dart
diff --git a/pkg/front_end/lib/src/fasta/scanner/utf8_bytes_scanner.dart b/pkg/front_end/lib/src/fasta/scanner/utf8_bytes_scanner.dart
index 98f3293c3d5c86d34b26e730a21e36c3ac522a9a..0f729000b496bb95dbbd4aefb87760ab5c83247f 100644
--- a/pkg/front_end/lib/src/fasta/scanner/utf8_bytes_scanner.dart
+++ b/pkg/front_end/lib/src/fasta/scanner/utf8_bytes_scanner.dart
@@ -87,7 +87,7 @@ class Utf8BytesScanner extends ArrayBasedScanner {
    * is not the case, the entire array is copied before scanning.
    */
   Utf8BytesScanner(this.bytes, {bool includeComments: false})
-      : super(includeComments) {
+      : super(includeComments, numberOfBytesHint: bytes.length) {
     assert(bytes.last == 0);
     // Skip a leading BOM.
     if (containsBomAt(0)) byteOffset += 3;