Add dart:io stubs to ddc sdk, define dart.library.html

pkg/dev_compiler/lib/src/compiler/compiler.dart

Index: pkg/dev_compiler/lib/src/compiler/compiler.dart
diff --git a/pkg/dev_compiler/lib/src/compiler/compiler.dart b/pkg/dev_compiler/lib/src/compiler/compiler.dart
index 4b954e185c4c234e28684f5a2f9b76c1a1bcc6b3..62921bd3ae3beb6b956b74b0658464d68c3751f4 100644
--- a/pkg/dev_compiler/lib/src/compiler/compiler.dart
+++ b/pkg/dev_compiler/lib/src/compiler/compiler.dart
@@ -97,6 +97,10 @@ class ModuleCompiler {
     options.declaredVariables.forEach(context.declaredVariables.define);
     context.declaredVariables.define('dart.isVM', 'false');
 
+    // TODO(vsm): Should this be hardcoded?

[Brian Wilkerson, 2016/12/14 20:28:41]

If you mean "hardcoded here" then I'd say this is fine, at least for now. There
was some discussion at one point of adding this information to the SDK (maybe in
the libraries.dart file?), but that hasn't happened yet as far as I know.

+    context.declaredVariables.define('dart.library.html', 'true');
+    context.declaredVariables.define('dart.library.io', 'false');
+
     return new ModuleCompiler.withContext(context, summaryData);
   }