No one uses SkPicture::swap.

tests/PictureTest.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapDevice.h"
 #include "SkBlurImageFilter.h"
 #include "SkCanvas.h"
@@ skipping 1543 matching lines @@
     // both pictures should have different ids
     REPORTER_ASSERT(reporter, hasData->uniqueID() != empty.uniqueID());
 
     // test out copy constructor
     SkPicture copyWithData(*hasData);
     REPORTER_ASSERT(reporter, hasData->uniqueID() == copyWithData.uniqueID());
 
     SkPicture emptyCopy(empty);
     REPORTER_ASSERT(reporter, empty.uniqueID() != emptyCopy.uniqueID());
 
-    // test out swap
-    {
-        SkPicture swapWithData;
-        uint32_t beforeID1 = swapWithData.uniqueID();
-        uint32_t beforeID2 = copyWithData.uniqueID();
-        swapWithData.swap(copyWithData);
-        REPORTER_ASSERT(reporter, copyWithData.uniqueID() == beforeID1);
-        REPORTER_ASSERT(reporter, swapWithData.uniqueID() == beforeID2);
-    }
-
     // test out clone
     {
         SkAutoTUnref<SkPicture> cloneWithData(hasData->clone());
         REPORTER_ASSERT(reporter, hasData->uniqueID() == cloneWithData->uniqueID());
 
         SkAutoTUnref<SkPicture> emptyClone(empty.clone());
         REPORTER_ASSERT(reporter, empty.uniqueID() != emptyClone->uniqueID());
     }
 }
 
@@ skipping 52 matching lines @@
     SkAutoTUnref<SkPicture> picture(recorder.endRecording());
 }
 
 DEF_TEST(Canvas_EmptyBitmap, r) {
     SkBitmap dst;
     dst.allocN32Pixels(10, 10);
     SkCanvas canvas(dst);
 
     test_draw_bitmaps(&canvas);
 }