Add constant info to the dart2js_info model

bin/debug_info.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.
 
 /// Tool used mainly by dart2js developers to debug the generated info and check
 /// that it is consistent and that it covers all the data we expect it to cover.
 library dart2js_info.bin.debug_info;
 
 import 'dart:convert';
 import 'dart:io';
@@ skipping 35 matching lines @@
     }
     if (diff2.length > 0) {
       _fail("some elements found in libraries weren't part of the global list"
           " (non-zero ${diff2.where((f) => f.size > 0).length})");
     }
   }
 
   // Validate that code-size adds up.
   int realTotal = info.program.size;
   int totalLib = info.libraries.fold(0, (n, lib) => n + lib.size);
-  if (totalLib != realTotal) {
-    var percent = ((realTotal - totalLib) * 100 / realTotal).toStringAsFixed(2);
-    _fail('$percent% size missing (sum of all libs < total)');
+  int constantsSize = info.constants.fold(0, (n, c) => n + c.size);
+  int accounted = totalLib + constantsSize;
+
+  if (accounted != realTotal) {
+    var percent = ((realTotal - accounted) * 100 / realTotal)
+        .toStringAsFixed(2);
+    _fail('$percent% size missing: $accounted (all libs + consts) '
+        '< $realTotal (total)');
   }
   var missingTotal = tracker.missing.values.fold(0, (a, b) => a + b);
   if (missingTotal > 0) {
     var percent = (missingTotal * 100 / realTotal).toStringAsFixed(2);
     _fail('$percent% size missing in libraries (sum of elements > lib.size)');
   }
 
   // Validate dependency data.
   compareGraphs(info);
 }
@@ skipping 179 matching lines @@
     _pass('dependency data is consistent');
   } else {
     _fail('inconsistencies in dependency data:\n'
         '   $inUsesNotInDependencies edges missing from "dependencies" graph\n'
         '   $inDependenciesNotInUses edges missing from "uses" graph');
   }
 }
 
 _pass(String msg) => print('\x1b[32mPASS\x1b[0m: $msg');
 _fail(String msg) => print('\x1b[31mFAIL\x1b[0m: $msg');