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 65742316c66ff25e990a162e3b8f69e1f1b68f9f..7898653b4e676ffafb619600c7f7b2818b8edfc3 100644
--- a/pkg/compiler/lib/src/elements/modelx.dart
+++ b/pkg/compiler/lib/src/elements/modelx.dart
@@ -225,9 +225,43 @@ 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 get isJsInterop => _jsInteropName != null;
+
+  void setJsInterop(String name) { _jsInteropName = name; }
+
+  bool get isNative => _isNative || isJsInterop;
+  bool get hasFixedBackendName => fixedBackendName != null || isJsInterop;
+
+  String _jsNameHelper(e) {

[sra1, 2015/10/01 20:55:27]

Element e
or some more specific type.

[Jacob, 2015/10/02 20:08:15]

Done.

+    if (e._jsInteropName != null && e._jsInteropName.isNotEmpty)
+      return e._jsInteropName;
+    return e.isLibrary ? 'self' : e.name;
+  }
+
+  String get fixedBackendName {
+    if (_fixedBackendName != null) return _fixedBackendName;
+    if (isJsInterop) {
+      return _jsNameHelper(isConstructor ? enclosingClass : this);
+    }
+    return null;
+  }
+
+  String get fixedBackendReceiver {

[sra1, 2015/10/01 20:55:27]

All this 'backend' logic must be in the js_backend.

[Jacob, 2015/10/02 20:08:15]

moved to js_backend/namer.dart

+    if (!isJsInterop) return null;
+    if (isInstanceMember) return 'this';
+    if (isConstructor) return enclosingClass.fixedBackendReceiver;
+    if (isLibrary) return 'self';
+    var sb = new StringBuffer();
+    sb..write(_jsNameHelper(library));
+
+    if (enclosingClass != null && enclosingClass != this) {
+      sb..write('.')..write(_jsNameHelper(enclosingClass));
+    }
+    return sb.toString();

[sra1, 2015/10/01 20:55:27]

So what is this computing?

[Jacob, 2015/10/02 20:08:15]

discussed offline and changed name to 
fixedBackendPath

+  }
+
   // Marks this element as a native element.
   void setNative(String name) {
     _isNative = true;
@@ -1802,6 +1836,20 @@ abstract class BaseFunctionElementX
     return functionSignatureCache;
   }
 
+  /**
+   * 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.
+   */
+  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.
@@ -2419,7 +2467,7 @@ abstract class BaseClassElementX extends ElementX
     return asInstanceOf(compiler.functionClass) != null || callType != null;
   }
 
-  bool get isNative => nativeTagInfo != null;
+  bool get isNative => nativeTagInfo != null || isJsInterop;
 
   void setNative(String name) {
     // TODO(johnniwinther): Assert that this is only called once. The memory