Infrastructure changes to support pull saveLayers forward task

src/core/SkPaintPriv.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPaintPriv.h"
 
 #include "SkBitmap.h"
@@ skipping 58 matching lines @@
                 SkColorFilter::kAlphaUnchanged_Flag) == 0)) {
                 break;
             }
             return true;
         default:
             break;
         }
     }
     return false;
 }
+
+bool NeedsDeepCopy(const SkPaint& paint) {
+    /*
+     *  These fields are known to be immutable, and so can be shallow-copied
+     *
+     *  getTypeface()
+     *  getAnnotation()
+     *  paint.getColorFilter()
+     *  getXfermode()
+     *  getPathEffect()
+     *  getMaskFilter()
+     */
+
+    return paint.getShader() ||
+#ifdef SK_SUPPORT_LEGACY_LAYERRASTERIZER_API
+           paint.getRasterizer() ||
+#endif
+           paint.getLooper() || // needs to hide its addLayer...
+           paint.getImageFilter();
+}
+