Fix TalkBack descriptions of keyboard shift mode transition

Bug: 14846348
Change-Id: I32435a31f919974a506e598d1f3cc1b55a0866ae

java/src/com/android/inputmethod/accessibility/MainKeyboardAccessibilityDelegate.java

@@ -156,14 +156,28 @@ public final class MainKeyboardAccessibilityDelegate
         case KeyboardId.ELEMENT_ALPHABET:
             if (lastElementId == KeyboardId.ELEMENT_ALPHABET
                     || lastElementId == KeyboardId.ELEMENT_ALPHABET_AUTOMATIC_SHIFTED) {
+                // Transition between alphabet mode and automatic shifted mode should be silently
+                // ignored because it can be determined by each key's talk back announce.
                 return;
             }
             resId = R.string.spoken_description_mode_alpha;
             break;
         case KeyboardId.ELEMENT_ALPHABET_MANUAL_SHIFTED:
+            if (lastElementId == KeyboardId.ELEMENT_ALPHABET_AUTOMATIC_SHIFTED) {
+                // Resetting automatic shifted mode by pressing the shift key causes the transition
+                // from automatic shifted to manual shifted that should be silently ignored.
+                return;
+            }
             resId = R.string.spoken_description_shiftmode_on;
             break;
         case KeyboardId.ELEMENT_ALPHABET_SHIFT_LOCK_SHIFTED:
+            if (lastElementId == KeyboardId.ELEMENT_ALPHABET_SHIFT_LOCKED) {
+                // Resetting caps locked mode by pressing the shift key causes the transition
+                // from shift locked to shift lock shifted that should be silently ignored.
+                return;
+            }
+            resId = R.string.spoken_description_shiftmode_locked;
+            break;
         case KeyboardId.ELEMENT_ALPHABET_SHIFT_LOCKED:
             resId = R.string.spoken_description_shiftmode_locked;
             break;