Restore old code style settings action (KT-23400)

Can't use `KotlinCodeStyleSettings` instead `KtCodeStyleSettings`,
because current `KotlinCodeStyleSettings` class is already used in third
party plugin.

idea/formatter/src/org/jetbrains/kotlin/idea/core/formatter/KotlinCodeStyleSettings.java

@@ -170,6 +170,10 @@ public class KotlinCodeStyleSettings extends CustomCodeStyleSettings {
         return tempSettings;
     }
 
+    public boolean canRestore() {
+        return settingsAgainstPreviousDefaults != null;
+    }
+
     public void restore() {
         if (settingsAgainstPreviousDefaults != null) {
             copyFrom(settingsAgainstPreviousDefaults);

idea/formatter/src/org/jetbrains/kotlin/idea/formatter/KotlinCommonCodeStyleSettings.java

@@ -231,6 +231,10 @@ public class KotlinCommonCodeStyleSettings extends CommonCodeStyleSettings {
         return provider == null ? null : provider.getSupportedFields();
     }
 
+    public boolean canRestore() {
+        return settingsAgainstPreviousDefaults != null;
+    }
+
     public void restore() {
         if (settingsAgainstPreviousDefaults != null) {
             CompatibilityKt.copyFromEx(this, settingsAgainstPreviousDefaults);

idea/formatter/src/org/jetbrains/kotlin/idea/formatter/KtCodeStyleSettings.kt

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2010-2018 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license
+ * that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.idea.formatter
+
+import com.intellij.openapi.project.Project
+import com.intellij.psi.codeStyle.CodeStyleSettingsManager
+import org.jetbrains.kotlin.idea.KotlinLanguage
+import org.jetbrains.kotlin.idea.core.formatter.KotlinCodeStyleSettings
+
+data class KtCodeStyleSettings(
+    val custom: KotlinCodeStyleSettings,
+    val common: KotlinCommonCodeStyleSettings
+)
+
+fun KtCodeStyleSettings.canRestore(): Boolean {
+    return custom.canRestore() || common.canRestore()
+}
+
+fun KtCodeStyleSettings.restore() {
+    custom.restore()
+    common.restore()
+}
+
+fun ktCodeStyleSettings(project: Project): KtCodeStyleSettings? {
+    @Suppress("DEPRECATION") // Suggested update is not supported in 173. BUNCH: 181
+    val settings = CodeStyleSettingsManager.getSettings(project)
+
+    val ktCommonSettings = settings.getCommonSettings(KotlinLanguage.INSTANCE) as KotlinCommonCodeStyleSettings
+    val ktCustomSettings = settings.getCustomSettings(KotlinCodeStyleSettings::class.java)
+
+    return KtCodeStyleSettings(ktCustomSettings, ktCommonSettings)
+}