suggest abstract in interface (IDEA-85701)

java/java-impl/src/com/intellij/codeInsight/completion/ModifierChooser.java

@@ -71,7 +71,7 @@ public class ModifierChooser {
     return addKeywords(list, inInterface ? new String[][]{
       new String[]{"public", "protected"},
       new String[]{"static"},
-      new String[]{"final"}
+      new String[]{"final", "abstract"}
     } : new String[][]{
       new String[]{"public", "protected", "private"},
       new String[]{"static"},

java/java-tests/testData/codeInsight/completion/keywords/abstractInInterface.java

@@ -0,0 +1,3 @@
+interface I {
+  <caret>
+}

java/java-tests/testSrc/com/intellij/codeInsight/completion/KeywordCompletionTest.java

@@ -90,6 +90,7 @@ public class KeywordCompletionTest extends LightCompletionTestCase {
   public void testNullInMethodCall() throws Exception { doTest(false); }
   public void testNullInMethodCall2() throws Exception { doTest(false); }
   public void testNewInMethodRefs() throws Exception { doTest(false); }
+  public void testAbstractInInterface() throws Exception { doTest(1, "abstract"); }
 
   public void testTryInExpression() throws Exception {
     configureByFile(BASE_PATH + "/" + getTestName(true) + ".java");