Fix const RegExp -> final RegExp in a dartdoc file.

sdk/lib/_internal/dartdoc/lib/src/markdown/block_parser.dart

Index: sdk/lib/_internal/dartdoc/lib/src/markdown/block_parser.dart
diff --git a/sdk/lib/_internal/dartdoc/lib/src/markdown/block_parser.dart b/sdk/lib/_internal/dartdoc/lib/src/markdown/block_parser.dart
index 6c5cff935cd6bdbb8c1110eb5a9d8b063433bca0..18f7d5a548b513126c982ac796bec60d463528c3 100644
--- a/sdk/lib/_internal/dartdoc/lib/src/markdown/block_parser.dart
+++ b/sdk/lib/_internal/dartdoc/lib/src/markdown/block_parser.dart
@@ -5,39 +5,39 @@
 part of markdown;
 
 /// The line contains only whitespace or is empty.
-const _RE_EMPTY = new RegExp(r'^([ \t]*)$');
+final _RE_EMPTY = new RegExp(r'^([ \t]*)$');
 
 /// A series of `=` or `-` (on the next line) define setext-style headers.
-const _RE_SETEXT = new RegExp(r'^((=+)|(-+))$');
+final _RE_SETEXT = new RegExp(r'^((=+)|(-+))$');
 
 /// Leading (and trailing) `#` define atx-style headers.
-const _RE_HEADER = new RegExp(r'^(#{1,6})(.*?)#*$');
+final _RE_HEADER = new RegExp(r'^(#{1,6})(.*?)#*$');
 
 /// The line starts with `>` with one optional space after.
-const _RE_BLOCKQUOTE = new RegExp(r'^[ ]{0,3}>[ ]?(.*)$');
+final _RE_BLOCKQUOTE = new RegExp(r'^[ ]{0,3}>[ ]?(.*)$');
 
 /// A line indented four spaces. Used for code blocks and lists.
-const _RE_INDENT = new RegExp(r'^(?:    |\t)(.*)$');
+final _RE_INDENT = new RegExp(r'^(?:    |\t)(.*)$');
 
 /// Three or more hyphens, asterisks or underscores by themselves. Note that
 /// a line like `----` is valid as both HR and SETEXT. In case of a tie,
 /// SETEXT should win.
-const _RE_HR = new RegExp(r'^[ ]{0,3}((-+[ ]{0,2}){3,}|'
+final _RE_HR = new RegExp(r'^[ ]{0,3}((-+[ ]{0,2}){3,}|'
                                  r'(_+[ ]{0,2}){3,}|'
                                  r'(\*+[ ]{0,2}){3,})$');
 
 /// Really hacky way to detect block-level embedded HTML. Just looks for
 /// "<somename".
-const _RE_HTML = new RegExp(r'^<[ ]*\w+[ >]');
+final _RE_HTML = new RegExp(r'^<[ ]*\w+[ >]');
 
 /// A line starting with one of these markers: `-`, `*`, `+`. May have up to
 /// three leading spaces before the marker and any number of spaces or tabs
 /// after.
-const _RE_UL = new RegExp(r'^[ ]{0,3}[*+-][ \t]+(.*)$');
+final _RE_UL = new RegExp(r'^[ ]{0,3}[*+-][ \t]+(.*)$');
 
 /// A line starting with a number like `123.`. May have up to three leading
 /// spaces before the marker and any number of spaces or tabs after.
-const _RE_OL = new RegExp(r'^[ ]{0,3}\d+\.[ \t]+(.*)$');
+final _RE_OL = new RegExp(r'^[ ]{0,3}\d+\.[ \t]+(.*)$');
 
 /// Maintains the internal state needed to parse a series of lines into blocks
 /// of markdown suitable for further inline parsing.