Prevent unhandled exception in NinePatchDrawable

Added null check in computeBitmapSize() to avoid unhandled
exception "java.lang.NullPointerException" at
android.graphics.Rect.<init>(Rect.java:72).

This problem was discovered in the wild.

Change-Id: I8a4729ceadcfc9744f11b8ceafdf24d6de88c645

Author: Sonia Serafimova

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

@@ -164,15 +164,17 @@ private void computeBitmapSize() {
                     sdensity, tdensity);
             mBitmapHeight = Bitmap.scaleFromDensity(mNinePatch.getHeight(),
                     sdensity, tdensity);
-            Rect dest = mPadding;
-            Rect src = mNinePatchState.mPadding;
-            if (dest == src) {
-                mPadding = dest = new Rect(src);
+            if (mNinePatchState.mPadding != null && mPadding != null) {
+                Rect dest = mPadding;
+                Rect src = mNinePatchState.mPadding;
+                if (dest == src) {
+                    mPadding = dest = new Rect(src);
+                }
+                dest.left = Bitmap.scaleFromDensity(src.left, sdensity, tdensity);
+                dest.top = Bitmap.scaleFromDensity(src.top, sdensity, tdensity);
+                dest.right = Bitmap.scaleFromDensity(src.right, sdensity, tdensity);
+                dest.bottom = Bitmap.scaleFromDensity(src.bottom, sdensity, tdensity);
             }
-            dest.left = Bitmap.scaleFromDensity(src.left, sdensity, tdensity);
-            dest.top = Bitmap.scaleFromDensity(src.top, sdensity, tdensity);
-            dest.right = Bitmap.scaleFromDensity(src.right, sdensity, tdensity);
-            dest.bottom = Bitmap.scaleFromDensity(src.bottom, sdensity, tdensity);
         }
     }