Support user generated custom native JS classes.

pkg/compiler/lib/src/elements/modelx.dart

Index: pkg/compiler/lib/src/elements/modelx.dart
diff --git a/pkg/compiler/lib/src/elements/modelx.dart b/pkg/compiler/lib/src/elements/modelx.dart
index f1d4c5bb04fe6dd1ea4afdecb656901fe57a8e12..129b2c37858b929ee234e43bcd9e4ed3ec3d4323 100644
--- a/pkg/compiler/lib/src/elements/modelx.dart
+++ b/pkg/compiler/lib/src/elements/modelx.dart
@@ -241,9 +241,45 @@ abstract class ElementX extends Element with ElementCommon {
 
   String _fixedBackendName = null;
   bool _isNative = false;
-  bool get isNative => _isNative;
-  bool get hasFixedBackendName => _fixedBackendName != null;
-  String get fixedBackendName => _fixedBackendName;
+  String _jsInteropName = null;
+  bool _isJsInterop = false;
+  bool get isJsInterop => _isJsInterop;

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

+ dartdoc

[Jacob, 2015/10/13 01:19:23]

Done.

+  String get jsInteropName => _jsInteropName;

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

+ dartdoc

[Jacob, 2015/10/13 01:19:23]

Done.

+
+  void setHasJsInterop() {

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

setIsJsInterop? (to match the field name)

markAsJsInterop()

[Jacob, 2015/10/13 01:19:22]

Done.

+    _isJsInterop = true;
+  }
+
+  void setJsInteropName(String name) {
+    assert(invariant(this,
+        _isJsInterop,
+        message: 'Element is not js interop but given a js interop name.'));
+    _jsInteropName = name;
+  }
+
+  bool get isNative => _isNative || isJsInterop;

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

questions/comments here:
 - now that this is more than _isNative, maybe it needs a dartdoc? (same below)
 - I noticed that you commonly make the distinction between the two in the rest
of the compiler, so I'm not sure how much are you gaining from adding `||
isJsInterop` here. I wonder if we can remove it here and explicitly check for it
where we are missing the check (maybe in type-inference?)

[Jacob, 2015/10/13 01:19:23]

There are a ton of places where the code paths are consistent. if you look
through the previous patches in this CL I started out with a top of checks for
isNative || isJsInterop but I reverted them as one point as I didn't hit all the
edge cases and for the most part they were treated the same. The main difference
is the name is the new js interop allows a bit more complex names. E.g.
"foo.bar.baz" rather than just "baz"

+  bool get hasFixedBackendName => fixedBackendName != null || isJsInterop;
+
+  String _jsNameHelper(Element e) {
+    if (e.jsInteropName != null && e.jsInteropName.isNotEmpty)

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

style nit: add braces

[Jacob, 2015/10/13 01:19:22]

Done.

+      return e.jsInteropName;
+    return e.isLibrary ? 'self' : e.name;
+  }
+
+  String get fixedBackendName {
+    if (_fixedBackendName != null) return _fixedBackendName;
+    if (isJsInterop) {
+      // If an element isJsInterop but _isJsInterop is false that means it is
+      // considered interop as the parent class is interop.
+      assert(invariant(this,
+          !(_isJsInterop &&  _jsInteropName == null),

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

should the check here also involve isConstructor like below? (or move the
invariant check to _jsNameHelper?

[Jacob, 2015/10/13 01:19:23]

done.

+          message: 'Element is js interop but js interop name has not yet been'
+          'computed.'));

[sra1, 2015/10/06 21:42:17]

I'd try and indent this like
 message:
     ' cccc'
     'ccc'

[Jacob, 2015/10/13 01:19:22]

Done.

+      return _jsNameHelper(isConstructor ? enclosingClass : this);

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

could we memoize the result by writting _fixedBackendName here?

[Jacob, 2015/10/13 01:19:22]

might as well. done.

+    }
+    return null;
+  }
+
   // Marks this element as a native element.
   void setNative(String name) {
     _isNative = true;
@@ -1986,6 +2022,20 @@ abstract class BaseFunctionElementX
     return functionSignatureCache;
   }
 
+  /**

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

nit, let's use /// (dart2js has both, but I'm trying to start moving towards
///)

[Jacob, 2015/10/13 01:19:22]

Done.

+   * An function is part of JsInterop if it has a jsInteropName annotation or it
+   * is an external class or top level member of a class or library tagged as
+   * JsInterop.

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

consider splitting the sentence into a set of bullets with each possible
scenario?

[Jacob, 2015/10/13 01:19:22]

Done.

+   */
+  bool get isJsInterop {
+    if (!isExternal) return false;
+
+    if (super.isJsInterop) return true;
+    if (isClassMember) return contextClass.isJsInterop;
+    if (isTopLevel) return library.isJsInterop;
+    return false;
+  }
+
   List<ParameterElement> get parameters {
     // TODO(johnniwinther): Store the list directly, possibly by using List
     // instead of Link in FunctionSignature.
@@ -2605,7 +2655,7 @@ abstract class BaseClassElementX extends ElementX
     return asInstanceOf(compiler.functionClass) != null || callType != null;
   }
 
-  bool get isNative => nativeTagInfo != null;
+  bool get isNative => nativeTagInfo != null || isJsInterop;

[Siggi Cherem (dart-lang), 2015/10/06 22:38:01]

same here

[Jacob, 2015/10/13 01:19:23]

The comment for the superclass still applies here so not sure it should be
commented here?

 
   void setNative(String name) {
     // TODO(johnniwinther): Assert that this is only called once. The memory