[Ongoing Call Chip] Improve accessibility.

Test: atest and manual
Bug: 183229367
Change-Id: I043f7259989c5431eeedc84488ae27fb08bc79c4

packages/SystemUI/res/layout/ongoing_call_chip.xml

@@ -23,6 +23,7 @@
     android:background="@drawable/ongoing_call_chip_bg"
     android:paddingStart="@dimen/ongoing_call_chip_side_padding"
     android:paddingEnd="@dimen/ongoing_call_chip_side_padding"
+    android:contentDescription="@string/ongoing_phone_call_content_description"
 >
 
     <ImageView

packages/SystemUI/res/values/strings.xml

@@ -2968,4 +2968,6 @@
     <!-- Message shown to suggest authentication using [CHAR LIMIT=60]-->
     <string name="keyguard_try_fingerprint">Use fingerprint to open</string>
 
+    <!-- Content description for a chip in the status bar showing that the user is currently on a phone call. [CHAR LIMIT=NONE] -->
+    <string name="ongoing_phone_call_content_description">Ongoing phone call</string>
 </resources>

packages/SystemUI/src/com/android/systemui/statusbar/phone/ongoingcall/OngoingCallChronometer.kt

@@ -56,6 +56,7 @@ class OngoingCallChronometer @JvmOverloads constructor(
         // call starts.
         minimumTextWidth = 0
         shouldHideText = false
+        visibility = VISIBLE
         super.setBase(base)
     }
 
@@ -76,6 +77,9 @@ class OngoingCallChronometer @JvmOverloads constructor(
 
         if (desiredTextWidth > enforcedTextWidth) {
             shouldHideText = true
+            // Changing visibility ensures that the content description is not read aloud when the
+            // time isn't displayed.
+            visibility = GONE
             setMeasuredDimension(0, 0)
         } else {
             // It's possible that the current text could fit in a smaller width, but we don't want