Handle toString on DOM types

pkg/dev_compiler/tool/input_sdk/private/js_helper.dart

Index: pkg/dev_compiler/tool/input_sdk/private/js_helper.dart
diff --git a/pkg/dev_compiler/tool/input_sdk/private/js_helper.dart b/pkg/dev_compiler/tool/input_sdk/private/js_helper.dart
index 578c724728d0b83303532825c4b0036e5e0f5096..44bc081819599f373896e3a5cd9267e070bb248e 100644
--- a/pkg/dev_compiler/tool/input_sdk/private/js_helper.dart
+++ b/pkg/dev_compiler/tool/input_sdk/private/js_helper.dart
@@ -192,9 +192,17 @@ class Primitives {
 
   /// In minified mode, uses the unminified names if available.

[Jennifer Messerly, 2017/06/23 18:27:11]

this one too

[vsm, 2017/06/26 20:29:24]

deleted

   static String objectToString(Object object) {
-    // String name = objectTypeName(object);
-    String name = JS('String', 'dart.typeName(dart.getReifiedType(#))', object);
-    return "Instance of '$name'";
+    bool nativeType = JS('bool', 'typeof # == "object" && !(# instanceof #)',

[Jennifer Messerly, 2017/06/23 18:27:11]

the normal way to check this is `getExtensionType`. Here's how dart.toString is
defined:

  var extension = getExtensionType(obj);
  if (extension != null) {
    return JS('String', '#[dartx.toString]()', obj);
  }

... this is used for all Object members. Should we change the pattern?

... also should we change dart.toString somehow? It seems like this code here
suggests we never want to fall back to Dart's Object.toString for native types
(unless the class defines it). So we're kinda dispatching to darx.toString, but
then we end up here and have to check again if we're a native type.

Instead, we could make sure native types don't get hooked up to dart:core
Object.toString in the first place. I'm not 100% sure how that happens without
poking around but it seems worth investigating?

[vsm, 2017/06/26 20:29:24]

Ahh, all our extension types (i think) extend Interceptor.  Moved the logic
there (see added-to-cl file).  If an extension defines its own toString, that
should be called.  Otherwise, Interceptor.toString should forward to JS before
we ever get here.

+        object, object, Object);
+    if (nativeType) {

[Jennifer Messerly, 2017/06/23 18:27:11]

very minor suggestion: if you put the conditional up here, I think it skips the
null check.

[vsm, 2017/06/26 20:29:24]

We already inferred nativeType as non-nullable.  Would have to define it as:

bool nativeType = JS('bool|Null', ....);

to allow null.   But killed the code anyway.  :-)

+      // Forward DOM types and other JS objects to their native toString method.
+      return JS('String', '#.toString()', object);
+    } else {
+      // Otherwise, fall back on default Object implemation.
+      String name =
+          JS('String', 'dart.typeName(dart.getReifiedType(#))', object);

[Jennifer Messerly, 2017/06/23 18:27:11]

can this just call `typeName(getReifiedType(object))` ... I don't think there's
anything special about dispatching through JS.

[vsm, 2017/06/26 20:29:24]

I was going to say we have no way to import our runtime - but it works!  Not
sure why I thought it didn't/wouldn't work.  :-)

+      return "Instance of '$name'";
+    }
   }
 
   static int dateNow() => JS('int', r'Date.now()');