Use variable length key (rather than accumulated matrix) as save layer hoisting key

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 "SkBBoxHierarchy.h"
 #include "SkBlurImageFilter.h"
 #include "SkCanvas.h"
@@ skipping 920 matching lines @@
         SkCanvas* c = recorder.beginRecording(SkIntToScalar(kWidth),
                                               SkIntToScalar(kHeight),
                                               &bbhFactory,
                                               SkPictureRecorder::kComputeSaveLayerInfo_RecordFlag);
         // 1)
         c->saveLayer(NULL, &complexPaint); // layer #0
         c->restore();
 
         // 2)
         c->saveLayer(NULL, NULL); // layer #1
-            c->translate(kWidth/2.0f, kHeight/2.0f);
+            c->translate(kWidth / 2.0f, kHeight / 2.0f);
             SkRect r = SkRect::MakeXYWH(0, 0, kWidth/2, kHeight/2);
             c->saveLayer(&r, &complexPaint); // layer #2
             c->restore();
         c->restore();
 
         // 3)
         {
             c->saveLayer(NULL, &complexPaint); // layer #3
             c->restore();
         }
@@ skipping 967 matching lines @@
 
     // The picture shares the immutable pixels but copies the mutable ones.
     REPORTER_ASSERT(r, mut.pixelRef()->unique());
     REPORTER_ASSERT(r, !immut.pixelRef()->unique());
 
     // When the picture goes away, it's just our bitmaps holding the refs.
     pic.reset(NULL);
     REPORTER_ASSERT(r, mut.pixelRef()->unique());
     REPORTER_ASSERT(r, immut.pixelRef()->unique());
 }