Make sure that Toast is always shown by Meta-Space.

It turns out that my previous CL [1] does not always show Toast when
Meta-Space is hit multiple times in a short period.  With this CL, we
attempt to make sure that the Toast is shown every time when Meta-Space
rotates the current IME subtype.

This CL also removes a rule that we do not show Toast when the IME
window has InputMethodService.IME_VISIBLE bit as it turns out to be
confusing.  In Android N, we just provide a consistent behavior
no matter the IME window is visible or not.

 [1]: If3fe17adbffe4c1125783fc77fed3cfe78fc7933
      ebda7d7ae1

Bug: 27547054
Bug: 28127795
Change-Id: I551c51cd672dba6e7693d23cb181007f51b0de9d

services/core/java/com/android/server/InputMethodManagerService.java

@@ -2966,16 +2966,6 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
                 return;
             }
             setInputMethodLocked(nextSubtype.mImi.getId(), nextSubtype.mSubtypeId);
-            if (mSubtypeSwitchedByShortCutToast != null) {
-                mSubtypeSwitchedByShortCutToast.cancel();
-                mSubtypeSwitchedByShortCutToast = null;
-            }
-            if ((mImeWindowVis & InputMethodService.IME_VISIBLE) != 0) {
-                // IME window is shown.  The user should be able to visually understand that the
-                // subtype is changed in most of cases.  To avoid UI overlap, we do not show a toast
-                // in this case.
-                return;
-            }
             final InputMethodInfo newInputMethodInfo = mMethodMap.get(mCurMethodId);
             if (newInputMethodInfo == null) {
                 return;
@@ -2983,8 +2973,12 @@ public class InputMethodManagerService extends IInputMethodManager.Stub
             final CharSequence toastText = InputMethodUtils.getImeAndSubtypeDisplayName(mContext,
                     newInputMethodInfo, mCurrentSubtype);
             if (!TextUtils.isEmpty(toastText)) {
-                mSubtypeSwitchedByShortCutToast = Toast.makeText(mContext, toastText.toString(),
-                        Toast.LENGTH_SHORT);
+                if (mSubtypeSwitchedByShortCutToast == null) {
+                    mSubtypeSwitchedByShortCutToast = Toast.makeText(mContext, toastText,
+                            Toast.LENGTH_SHORT);
+                } else {
+                    mSubtypeSwitchedByShortCutToast.setText(toastText);
+                }
                 mSubtypeSwitchedByShortCutToast.show();
             }
         }