Clean up NinePatch(Drawable) for mainline module

Bug: 155661807
Test: make

Document/remove @hide/@UnsupportedAppUsage from NinePatch(Drawable)
- Remove the unused copy constructor
- Remove @UnsupportedAppUsage from InsetStruct. No usage was shown on
  the dashboard; it was likely added by mistake due to its being called
  from JNI
- Document that the other @hide methods are needed for access from
  outside the package, but still within the module.

Change-Id: Ia27a5eda63a0115da54225f7ac18b3d2a55ab01f

graphics/java/android/graphics/NinePatch.java

@@ -39,11 +39,10 @@ public class NinePatch {
      * Present on a 9 patch bitmap if it optical insets were manually included,
      * or if outline insets were automatically included by aapt.
      *
-     * @hide
+     * @hide For use by NinePatchDrawable, but must not be used outside the module.
      */
     public static class InsetStruct {
         @SuppressWarnings({"UnusedDeclaration"}) // called from JNI
-        @UnsupportedAppUsage
         InsetStruct(int opticalLeft, int opticalTop, int opticalRight, int opticalBottom,
                 int outlineLeft, int outlineTop, int outlineRight, int outlineBottom,
                 float outlineRadius, int outlineAlpha, float decodeScale) {
@@ -86,7 +85,7 @@ public class NinePatch {
     /**
      * Used by native code. This pointer is an instance of Res_png_9patch*.
      *
-     * @hide
+     * @hide for use by android.graphics, but must not be used outside the module.
      */
     @UnsupportedAppUsage
     public long mNativeChunk;
@@ -119,20 +118,6 @@ public class NinePatch {
         mNativeChunk = validateNinePatchChunk(chunk);
     }
 
-    /**
-     * @hide
-     */
-    public NinePatch(NinePatch patch) {
-        mBitmap = patch.mBitmap;
-        mSrcName = patch.mSrcName;
-        if (patch.mPaint != null) {
-            mPaint = new Paint(patch.mPaint);
-        }
-        // No need to validate the 9patch chunk again, it was done by
-        // the instance we're copying from
-        mNativeChunk = patch.mNativeChunk;
-    }
-
     @Override
     protected void finalize() throws Throwable {
         try {

graphics/java/android/graphics/drawable/NinePatchDrawable.java

@@ -114,7 +114,7 @@ public class NinePatchDrawable extends Drawable {
      * Create drawable from raw nine-patch data, setting initial target density
      * based on the display metrics of the resources.
      *
-     * @hide
+     * @hide for use by android.graphics.ImageDecoder, but must not be used outside the module.
      */
     public NinePatchDrawable(Resources res, Bitmap bitmap, byte[] chunk,
             Rect padding, Rect opticalInsets, String srcName) {