Revert "[dartdevc] Fixing issue related to dual exports of multiple entrypoints in a cyclic import loop."

This reverts commit 53895b2.

Reason for revert: Replacing this change with a new strategy for better module reordering.

Original change's description:
> [dartdevc] Fixing issue related to dual exports of multiple entrypoints in a cyclic import loop.
>
> See: flutter/flutter#64011
> Change-Id: I8a11e9d3f19428a516cf7a60ee45c3bacf26545d
> Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/162383
> Commit-Queue: Mark Zhou <[email protected]>
> Reviewed-by: Nicholas Shahan <[email protected]>

[email protected],[email protected],[email protected]

# Not skipping CQ checks because original CL landed > 1 day ago.

Change-Id: Iee91d33d1696ffa7406b724466144ab06af80394
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/165873
Commit-Queue: Mark Zhou <[email protected]>
Reviewed-by: Mark Zhou <[email protected]>
Reviewed-by: Sigmund Cherem <[email protected]>

Author: Markzipan

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

@@ -882,21 +882,16 @@ class ProgramCompiler extends ComputeOnceConstantVisitor<js_ast.Expression>
     var savedTopLevelClass = _classEmittingExtends;
     _classEmittingExtends = c;
 
-    // Refers to 'S' in `class C extends S`. Set this to null to avoid
-    // referencing deferred supertypes in _emitClassConstructor's JS output.
-    js_ast.Expression baseClass;
-
+    // Unroll mixins.
     if (shouldDefer(supertype)) {
       deferredSupertypes.add(runtimeStatement('setBaseClass(#, #)', [
         getBaseClass(isMixinAliasClass(c) ? 0 : mixinApplications.length),
         emitDeferredType(supertype),
       ]));
-      // Refers to 'supertype' without any type arguments.
       supertype =
           _coreTypes.rawType(supertype.classNode, _currentLibrary.nonNullable);
-    } else {
-      baseClass = emitClassRef(supertype);
     }
+    var baseClass = emitClassRef(supertype);
 
     if (isMixinAliasClass(c)) {
       // Given `class C = Object with M [implements I1, I2 ...];`