Revert[2] of "add backdrop option to SaveLayerRec"

src/core/SkRecordOpts.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRecordOpts.h"
 
 #include "SkRecordPattern.h"
@@ skipping 159 matching lines @@
     // Run until they stop changing things.
     while (apply(&onlyDraws, record) || apply(&noDraws, record));
 }
 
 // For some SaveLayer-[drawing command]-Restore patterns, merge the SaveLayer's alpha into the
 // draw, and no-op the SaveLayer and Restore.
 struct SaveLayerDrawRestoreNooper {
     typedef Pattern<Is<SaveLayer>, IsDraw, Is<Restore>> Match;
 
     bool onMatch(SkRecord* record, Match* match, int begin, int end) {
+        if (match->first<SaveLayer>()->backdrop) {
+            // can't throw away the layer if we have a backdrop
+            return false;
+        }
+
         // A SaveLayer's bounds field is just a hint, so we should be free to ignore it.
         SkPaint* layerPaint = match->first<SaveLayer>()->paint;
         if (nullptr == layerPaint) {
             // There wasn't really any point to this SaveLayer at all.
             return KillSaveLayerAndRestore(record, begin);
         }
 
         SkPaint* drawPaint = match->second<SkPaint>();
         if (drawPaint == nullptr) {
             // We can just give the draw the SaveLayer's paint.
@@ skipping 27 matching lines @@
       SaveLayer (typically for SVG filter)
       Restore
     Restore
   Restore
 */
 struct SvgOpacityAndFilterLayerMergePass {
     typedef Pattern<Is<SaveLayer>, Is<Save>, Is<ClipRect>, Is<SaveLayer>,
                     Is<Restore>, Is<Restore>, Is<Restore>> Match;
 
     bool onMatch(SkRecord* record, Match* match, int begin, int end) {
+        if (match->first<SaveLayer>()->backdrop) {
+            // can't throw away the layer if we have a backdrop
+            return false;
+        }
+
         SkPaint* opacityPaint = match->first<SaveLayer>()->paint;
         if (nullptr == opacityPaint) {
             // There wasn't really any point to this SaveLayer at all.
             return KillSaveLayerAndRestore(record, begin);
         }
 
         // This layer typically contains a filter, but this should work for layers with for other
         // purposes too.
         SkPaint* filterLayerPaint = match->fourth<SaveLayer>()->paint;
         if (filterLayerPaint == nullptr) {
@@ skipping 39 matching lines @@
 
 void SkRecordOptimize2(SkRecord* record) {
     multiple_set_matrices(record);
     SkRecordNoopSaveRestores(record);
     SkRecordNoopSaveLayerDrawRestores(record);
     SkRecordMergeSvgOpacityAndFilterLayers(record);
 
     record->defrag();
 }