dart2js: don't emit big integers as integer, but instead use their exponential representation.

tests/compiler/dart2js/number_output_test.dart

+// Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "package:expect/expect.dart";
+import "package:async_helper/async_helper.dart";
+import 'memory_compiler.dart';
+
+const MEMORY_SOURCE_FILES = const {
+    'main.dart': '''
+        main() {
+          print(12300000);
+          print(1234567890123456789012345);
+          print(double.MAX_FINITE);
+        }'''};
+
+void main() {
+  OutputCollector collector = new OutputCollector();
+  var compiler = compilerFor(MEMORY_SOURCE_FILES, outputProvider: collector);
+  asyncTest(() => compiler.run(Uri.parse('memory:main.dart')).then((_) {
+    // Check that we use the shorter exponential representations.
+    String jsOutput = collector.getOutput('', 'js');
+
+    Expect.isTrue(jsOutput.contains('1.23e+7')); // Shorter than 12300000.

[sra1, 2015/02/20 17:02:54]

123e5 would be better

[floitsch, 2015/02/20 20:23:20]

https://codereview.chromium.org/938323003

+    Expect.isTrue(jsOutput.contains('1.2345678901234568e+24'));
+    Expect.isTrue(jsOutput.contains('1.7976931348623157e+308'));
+    Expect.isFalse(jsOutput.contains('12300000'));
+    Expect.isFalse(jsOutput.contains('1234567890123456789012345'));
+    // The decimal expansion of double.MAX_FINITE has 308 digits. We only check
+    // for its prefix.
+    Expect.isFalse(jsOutput.contains('179769313486231570814527423731'));
+  }));
+}