Hide MeasuredText.getChars

The MeasuredText.getChars is used only from text layout internals:
- LineBreaker#computeLineBreaks
- Canvas.drawtextRun

Thus, no need to be exposed to public. Making it @hide

Change-Id: I7c27a4b95d7d5ebc2ad5d74c947cdea3ce08f2ab
Fix: 124795470
Test: N/A

api/current.txt

@@ -15953,7 +15953,6 @@ package android.graphics.text {
   public class MeasuredText {
     method public void getBounds(@IntRange(from=0) int, @IntRange(from=0) int, @NonNull android.graphics.Rect);
     method @FloatRange(from=0.0f) @Px public float getCharWidthAt(@IntRange(from=0) int);
-    method @NonNull public char[] getChars();
     method @FloatRange(from=0.0) @Px public float getWidth(@IntRange(from=0) int, @IntRange(from=0) int);
   }
 

graphics/java/android/graphics/text/MeasuredText.java

@@ -65,6 +65,7 @@ public class MeasuredText {
 
     /**
      * Returns the characters in the paragraph used to compute this MeasuredText instance.
+     * @hide
      */
     public @NonNull char[] getChars() {
         return mChars;