Improve a11y for BiometricPrompt credential view

Ensures text that is important for accessibility in the auth prompt
credential view is read aloud by TalkBack.

Test: Manual:
1. Set PIN/pattern/password as screen unlock method
3. Enable Talkback in settings
4. Launch the CtsVerifier-v2 test app
5. Open SECURITY > Biometric Tests > BIOMETRIC+CREDENTIAL TESTS
6. Tap 4a: SetUserAuthParams: Credential, Cipher
7. Tap Choose Unlock time-based key with credential
8. Enter an incorrect PIN/pattern/password

Fixes: 151389440
Fixes: 151390960
Change-Id: I95c38cb678b0ae46988539b167c48fe9572677bc

packages/SystemUI/res/values/styles.xml

@@ -249,6 +249,7 @@
     <style name="TextAppearance.DeviceManagementDialog.Title" parent="@android:style/TextAppearance.DeviceDefault.DialogWindowTitle"/>
 
     <style name="TextAppearance.AuthCredential">
+        <item name="android:accessibilityLiveRegion">polite</item>
         <item name="android:gravity">center_horizontal</item>
         <item name="android:textAlignment">gravity</item>
         <item name="android:layout_gravity">top</item>

packages/SystemUI/src/com/android/systemui/biometrics/AuthCredentialView.java

@@ -214,9 +214,11 @@ public abstract class AuthCredentialView extends LinearLayout {
     protected void onAttachedToWindow() {
         super.onAttachedToWindow();
 
-        setText(mTitleView, getTitle(mBiometricPromptBundle));
+        final CharSequence title = getTitle(mBiometricPromptBundle);
+        setText(mTitleView, title);
         setTextOrHide(mSubtitleView, getSubtitle(mBiometricPromptBundle));
         setTextOrHide(mDescriptionView, getDescription(mBiometricPromptBundle));
+        announceForAccessibility(title);
 
         final boolean isManagedProfile = Utils.isManagedProfile(mContext, mEffectiveUserId);
         final Drawable image;