Land Alexander's change that turns assert into a keyword.

lib/compiler/implementation/scanner/parser.dart

Index: lib/compiler/implementation/scanner/parser.dart
diff --git a/lib/compiler/implementation/scanner/parser.dart b/lib/compiler/implementation/scanner/parser.dart
index b2faf1a83e517f1e19e9451db7c4197170e4a1f0..a276ebe35de96216d1b6e693104990ae97489a6b 100644
--- a/lib/compiler/implementation/scanner/parser.dart
+++ b/lib/compiler/implementation/scanner/parser.dart
@@ -1149,6 +1149,8 @@ class Parser {
       return parseBreakStatement(token);
     } else if (value === 'continue') {
       return parseContinueStatement(token);
+    } else if (value === 'assert') {
+      return parseAssertStatement(token);
     } else if (value === ';') {
       return parseEmptyStatement(token);
     } else if (value === 'const') {
@@ -2130,6 +2132,14 @@ class Parser {
     return expectSemicolon(token);
   }
 
+  Token parseAssertStatement(Token token) {
+    Token assertKeyword = token;
+    token = expect('assert', token);
+    token = parseArguments(token);
+    listener.handleAssertStatement(assertKeyword, token);
+    return expectSemicolon(token);
+  }
+
   Token parseContinueStatement(Token token) {
     assert(optional('continue', token));
     Token continueKeyword = token;