Improve search indexing time.

- Some import clean up.
- Add timing log to track indexing time breakdown.
- Remove isAvailable() from UserDictionaryPreferenceController.

Bug: 36391685
Test: rebuild
Change-Id: If154c5dafba5d21cb1020497c44fbf67f03ad820

tests/robotests/src/com/android/settings/language/UserDictionaryPreferenceControllerTest.java

@@ -56,16 +56,7 @@ public class UserDictionaryPreferenceControllerTest {
     }
 
     @Test
-    public void testIsAvailable_noLocale_shouldReturnFalse() {
-        mController.mLocales = null;
-
-        assertThat(mController.isAvailable()).isFalse();
-    }
-
-    @Test
-    public void testIsAvailable_hasLocale_shouldReturnTrue() {
-        mController.mLocales.add("en");
-
+    public void testIsAvailable_shouldReturnTrue() {
         assertThat(mController.isAvailable()).isTrue();
     }