Split the Kernel transformations into modular and global ones

pkg/kernel/lib/transformations/mixin_full_resolution.dart

Index: pkg/kernel/lib/transformations/mixin_full_resolution.dart
diff --git a/pkg/kernel/lib/transformations/mixin_full_resolution.dart b/pkg/kernel/lib/transformations/mixin_full_resolution.dart
index b045ee6b511defbdb1c0bc288ce20edc6f615cf7..92ed3b7685e502e92bcf3d573ddd79747acb2e70 100644
--- a/pkg/kernel/lib/transformations/mixin_full_resolution.dart
+++ b/pkg/kernel/lib/transformations/mixin_full_resolution.dart
@@ -31,6 +31,8 @@ class MixinFullResolution {
     // the mixin and constructors from the base class.
     var processedClasses = new Set<Class>();
     for (var library in program.libraries) {
+      if (library.isExternal) continue;
+
       for (var class_ in library.classes) {
         transformClass(processedClasses, transformedClasses, class_);
       }
@@ -41,6 +43,8 @@ class MixinFullResolution {
 
     // Resolve all super call expressions and super initializers.
     for (var library in program.libraries) {
+      if (library.isExternal) continue;
+
       for (var class_ in library.classes) {
         final bool hasTransformedSuperclass =
             transformedClasses.contains(class_.superclass);
@@ -82,6 +86,12 @@ class MixinFullResolution {
     // constructors in this class.
     if (!class_.isMixinApplication) return;
 
+    if (class_.mixedInClass.level != ClassLevel.Body) {
+      throw new Exception(
+          'Class "${class_.name}" mixes in "${class_.mixedInClass.name}" from'
+          ' an external library.  Did you forget --link?');
+    }
+
     transformedClasses.add(class_);
 
     // Clone fields and methods from the mixin class.