Improve AddInitKeyword quickfix

- Extract quickfix method
- Delete redundant semicolon
- Do not replace initializer PSI element

compiler/frontend/src/org/jetbrains/kotlin/psi/JetClassInitializer.java

@@ -58,6 +58,11 @@ public class JetClassInitializer extends JetDeclarationStub<KotlinPlaceHolderStu
     }
 
     public boolean hasInitKeyword() {
-        return findChildByType(JetTokens.INIT_KEYWORD) != null;
+        return getInitKeyword() != null;
+    }
+
+    @Nullable
+    public PsiElement getInitKeyword() {
+        return findChildByType(JetTokens.INIT_KEYWORD);
     }
 }

compiler/frontend/src/org/jetbrains/kotlin/psi/JetPsiFactory.kt

@@ -230,9 +230,11 @@ public class JetPsiFactory(private val project: Project) {
     }
 
     public fun createAnonymousInitializer(): JetClassInitializer {
-        return createClass("class A { {} }").getAnonymousInitializers().first()
+        return createClass("class A { init {} }").getAnonymousInitializers().first()
     }
 
+    public fun createInitKeyword(): PsiElement = createAnonymousInitializer().getInitKeyword()!!
+
     public fun createEmptyClassBody(): JetClassBody {
         return createClass("class A(){}").getBody()!!
     }

compiler/frontend/src/org/jetbrains/kotlin/psi/psiUtil/jetPsiUtil.kt

@@ -408,6 +408,14 @@ public fun PsiElement.prevLeafSkipWhitespacesAndComments(): PsiElement? {
     return leaf
 }
 
+public fun PsiElement.prevLeafSkipWhitespaces(): PsiElement? {
+    var leaf = prevLeaf()
+    while (leaf is PsiWhiteSpace) {
+        leaf = leaf!!.prevLeaf()
+    }
+    return leaf
+}
+
 public fun PsiElement.nextLeafSkipWhitespacesAndComments(): PsiElement? {
     var leaf = nextLeaf()
     while (leaf is PsiWhiteSpace || leaf is PsiComment) {