Effects on the paint also prevent layer merge optimization.

src/core/SkPictureRecord.cpp

 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkPictureRecord.h"
 #include "SkTSearch.h"
 #include "SkPixelRef.h"
@@ skipping 409 matching lines @@
 
     // For this optimization we only fold the saveLayer and drawBitmapRect
     // together if the saveLayer's draw is simple (i.e., no fancy effects) and
     // and the only difference in the colors is that the saveLayer's can have
     // an alpha while the drawBitmapRect's is opaque.
     // TODO: it should be possible to fold them together even if they both
     // have different non-255 alphas
     SkColor layerColor = saveLayerPaint->getColor() | 0xFF000000; // force opaque
 
     SkAutoTDelete<SkPaint> dbmPaint(paintDict->unflatten(dbmPaintId));
-    if (NULL == dbmPaint.get() || dbmPaint->getColor() != layerColor) {
+    if (NULL == dbmPaint.get() || dbmPaint->getColor() != layerColor || !is_simple(*dbmPaint)) {
         return false;
     }
 
     SkColor newColor = SkColorSetA(dbmPaint->getColor(),
                                    SkColorGetA(saveLayerPaint->getColor()));
     dbmPaint->setColor(newColor);
 
     const SkFlatData* data = paintDict->findAndReturnFlat(*dbmPaint);
     if (NULL == data) {
         return false;
@@ skipping 1385 matching lines @@
 void SkPictureRecord::validateRegions() const {
     int count = fRegions.count();
     SkASSERT((unsigned) count < 0x1000);
     for (int index = 0; index < count; index++) {
         const SkFlatData* region = fRegions[index];
         SkASSERT(region);
 //        region->validate();
     }
 }
 #endif