Fix rendering artifacts in pull-saveLayers-forward mode

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"
 #if SK_SUPPORT_GPU
 #include "SkBlurImageFilter.h"
@@ skipping 871 matching lines @@
         REPORTER_ASSERT(reporter, kWidth == info1.fSize.fWidth && kHeight == info1.fSize.fHeight);
         REPORTER_ASSERT(reporter, info1.fCTM.isIdentity());
         REPORTER_ASSERT(reporter, 0 == info1.fOffset.fX && 0 == info1.fOffset.fY);
         REPORTER_ASSERT(reporter, NULL != info1.fPaint);
         REPORTER_ASSERT(reporter, !info1.fIsNested && info1.fHasNestedLayers); // has a nested SL
 
         REPORTER_ASSERT(reporter, info2.fValid);
         REPORTER_ASSERT(reporter, kWidth/2 == info2.fSize.fWidth &&
                                   kHeight/2 == info2.fSize.fHeight); // bound reduces size
         REPORTER_ASSERT(reporter, info2.fCTM.isIdentity());         // translated
-        REPORTER_ASSERT(reporter, 0 == info2.fOffset.fX && 0 == info2.fOffset.fY);
+        REPORTER_ASSERT(reporter, kWidth/2 == info2.fOffset.fX && 
+                                  kHeight/2 == info2.fOffset.fY);
         REPORTER_ASSERT(reporter, NULL != info1.fPaint);
         REPORTER_ASSERT(reporter, info2.fIsNested && !info2.fHasNestedLayers); // is nested
 
         REPORTER_ASSERT(reporter, info3.fValid);
         REPORTER_ASSERT(reporter, kWidth == info3.fSize.fWidth && kHeight == info3.fSize.fHeight);
         REPORTER_ASSERT(reporter, info3.fCTM.isIdentity());
         REPORTER_ASSERT(reporter, 0 == info3.fOffset.fX && 0 == info3.fOffset.fY);
         REPORTER_ASSERT(reporter, NULL != info3.fPaint);
         REPORTER_ASSERT(reporter, !info3.fIsNested && !info3.fHasNestedLayers);
 
@@ skipping 557 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);
 }