[IR] Remove JS-specific manglers, as they don't customize any behavior

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/mangle/descriptor/DescriptorMangleComputer.kt

@@ -18,7 +18,7 @@ import org.jetbrains.kotlin.types.typeUtil.isUnit
 /**
  * The descriptor-based mangle computer. Used to compute a mangled name for a declaration given its [DeclarationDescriptor].
  */
-abstract class DescriptorMangleComputer(builder: StringBuilder, mode: MangleMode) :
+open class DescriptorMangleComputer(builder: StringBuilder, mode: MangleMode) :
     BaseKotlinMangleComputer<
             /*Declaration=*/DeclarationDescriptor,
             /*Type=*/KotlinType,
@@ -30,7 +30,7 @@ abstract class DescriptorMangleComputer(builder: StringBuilder, mode: MangleMode
             >(builder, mode) {
     final override fun getTypeSystemContext(session: Nothing?): TypeSystemContext = SimpleClassicTypeSystemContext
 
-    abstract override fun copy(newMode: MangleMode): DescriptorMangleComputer
+    override fun copy(newMode: MangleMode) = DescriptorMangleComputer(builder, newMode)
 
     final override fun DeclarationDescriptor.visitParent() {
         containingDeclaration?.visit()

compiler/ir/serialization.common/src/org/jetbrains/kotlin/backend/common/serialization/mangle/ir/IrMangleComputer.kt

@@ -19,7 +19,7 @@ import org.jetbrains.kotlin.ir.visitors.acceptVoid
 /**
  * A mangle computer that generates a mangled name for a Kotlin declaration represented by [IrDeclaration].
  */
-abstract class IrMangleComputer(
+open class IrMangleComputer(
     builder: StringBuilder,
     mode: MangleMode,
     protected val compatibleMode: Boolean
@@ -40,7 +40,7 @@ abstract class IrMangleComputer(
 
     open fun IrFunction.platformSpecificFunctionMarks(): List<String> = emptyList()
 
-    abstract override fun copy(newMode: MangleMode): IrMangleComputer
+    override fun copy(newMode: MangleMode) = IrMangleComputer(builder, newMode, compatibleMode)
 
     final override fun IrDeclaration.visitParent() {
         parent.acceptVoid(Visitor())

compiler/ir/serialization.js/src/org/jetbrains/kotlin/ir/backend/js/lower/serialization/ir/JsMangler.kt

@@ -23,14 +23,10 @@ abstract class AbstractJsManglerIr : IrBasedKotlinManglerImpl() {
         override fun IrDeclaration.isPlatformSpecificExported() = false
     }
 
-    private class JsIrManglerComputer(builder: StringBuilder, mode: MangleMode, compatibleMode: Boolean) : IrMangleComputer(builder, mode, compatibleMode) {
-        override fun copy(newMode: MangleMode): IrMangleComputer = JsIrManglerComputer(builder, newMode, compatibleMode)
-    }
-
     override fun getExportChecker(compatibleMode: Boolean): KotlinExportChecker<IrDeclaration> = JsIrExportChecker(compatibleMode)
 
     override fun getMangleComputer(mode: MangleMode, compatibleMode: Boolean): KotlinMangleComputer<IrDeclaration> {
-        return JsIrManglerComputer(StringBuilder(256), mode, compatibleMode)
+        return IrMangleComputer(StringBuilder(256), mode, compatibleMode)
     }
 }
 
@@ -46,14 +42,10 @@ abstract class AbstractJsDescriptorMangler : DescriptorBasedKotlinManglerImpl()
         override fun DeclarationDescriptor.isPlatformSpecificExported() = false
     }
 
-    private class JsDescriptorManglerComputer(builder: StringBuilder, mode: MangleMode) : DescriptorMangleComputer(builder, mode) {
-        override fun copy(newMode: MangleMode): DescriptorMangleComputer = JsDescriptorManglerComputer(builder, newMode)
-    }
-
     override fun getExportChecker(compatibleMode: Boolean): KotlinExportChecker<DeclarationDescriptor> = exportChecker
 
     override fun getMangleComputer(mode: MangleMode, compatibleMode: Boolean): KotlinMangleComputer<DeclarationDescriptor> {
-        return JsDescriptorManglerComputer(StringBuilder(256), mode)
+        return DescriptorMangleComputer(StringBuilder(256), mode)
     }
 }