Do not register OnBackInvokedCallback for SoftInputWindow.

By default Dialog#onStart will register onBackInvokedCallback, which
should be necessary since InputMethodService will register
CompatOnBackInvokedCallback for input method window.

Bug: 294162707
Test: atest BackGestureInvokedTest
Test: manual, launch Calendar then trigger back several times, verify
the back gesture can close app normally.

Change-Id: Icacfef60666fba1522f9d0f4ddc47e74a4560a32

core/java/android/app/Dialog.java

@@ -454,12 +454,11 @@ public class Dialog implements DialogInterface, Window.Callback,
      */
     protected void onStart() {
         if (mActionBar != null) mActionBar.setShowHideAnimationEnabled(true);
-        if (mContext != null
+        if (allowsRegisterDefaultOnBackInvokedCallback() && mContext != null
                 && WindowOnBackInvokedDispatcher.isOnBackInvokedCallbackEnabled(mContext)) {
             // Add onBackPressed as default back behavior.
             mDefaultBackCallback = this::onBackPressed;
             getOnBackInvokedDispatcher().registerSystemOnBackInvokedCallback(mDefaultBackCallback);
-            mDefaultBackCallback = null;
         }
     }
 
@@ -470,9 +469,18 @@ public class Dialog implements DialogInterface, Window.Callback,
         if (mActionBar != null) mActionBar.setShowHideAnimationEnabled(false);
         if (mDefaultBackCallback != null) {
             getOnBackInvokedDispatcher().unregisterOnBackInvokedCallback(mDefaultBackCallback);
+            mDefaultBackCallback = null;
         }
     }
 
+    /**
+     * Whether this dialog allows to register the default onBackInvokedCallback.
+     * @hide
+     */
+    protected boolean allowsRegisterDefaultOnBackInvokedCallback() {
+        return true;
+    }
+
     private static final String DIALOG_SHOWING_TAG = "android:dialogShowing";
     private static final String DIALOG_HIERARCHY_TAG = "android:dialogHierarchy";
 
@@ -697,7 +705,8 @@ public class Dialog implements DialogInterface, Window.Callback,
         if (event.isTracking() && !event.isCanceled()) {
             switch (keyCode) {
                 case KeyEvent.KEYCODE_BACK:
-                    if (!WindowOnBackInvokedDispatcher.isOnBackInvokedCallbackEnabled(mContext)) {
+                    if (!WindowOnBackInvokedDispatcher.isOnBackInvokedCallbackEnabled(mContext)
+                            || !allowsRegisterDefaultOnBackInvokedCallback()) {
                         onBackPressed();
                         return true;
                     }

core/java/android/inputmethodservice/SoftInputWindow.java

@@ -79,6 +79,13 @@ final class SoftInputWindow extends Dialog {
     @WindowState
     private int mWindowState = WindowState.TOKEN_PENDING;
 
+    @Override
+    protected boolean allowsRegisterDefaultOnBackInvokedCallback() {
+        // Do not register OnBackInvokedCallback from Dialog#onStart, InputMethodService will
+        // register CompatOnBackInvokedCallback for input method window.
+        return false;
+    }
+
     /**
      * Set {@link IBinder} window token to the window.
      *