add backdrop option to SaveLayerRec

include/core/SkCanvas.h

 /*
  * Copyright 2006 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvas_DEFINED
 #define SkCanvas_DEFINED
 
@@ skipping 404 matching lines @@
         kIsOpaque_SaveLayerFlag         = 1 << 0,
         kPreserveLCDText_SaveLayerFlag  = 1 << 1,
 
 #ifdef SK_SUPPORT_LEGACY_CLIPTOLAYERFLAG
         kDontClipToLayer_Legacy_SaveLayerFlag = kDontClipToLayer_PrivateSaveLayerFlag,
 #endif
     };
     typedef uint32_t SaveLayerFlags;
 
     struct SaveLayerRec {
-        SaveLayerRec() : fBounds(nullptr), fPaint(nullptr), fSaveLayerFlags(0) {}
+        SaveLayerRec()
+            : fBounds(nullptr), fPaint(nullptr), fBackdrop(nullptr), fSaveLayerFlags(0)
+        {}
         SaveLayerRec(const SkRect* bounds, const SkPaint* paint, SaveLayerFlags saveLayerFlags = 0)
             : fBounds(bounds)
             , fPaint(paint)
+            , fBackdrop(nullptr)
+            , fSaveLayerFlags(saveLayerFlags)
+        {}
+        SaveLayerRec(const SkRect* bounds, const SkPaint* paint, const SkImageFilter* backdrop,
+                     SaveLayerFlags saveLayerFlags)
+            : fBounds(bounds)
+            , fPaint(paint)
+            , fBackdrop(backdrop)
             , fSaveLayerFlags(saveLayerFlags)
         {}
 
-        const SkRect*   fBounds;    // optional
-        const SkPaint*  fPaint;     // optional
-        SaveLayerFlags  fSaveLayerFlags;
+        const SkRect*           fBounds;    // optional
+        const SkPaint*          fPaint;     // optional
+        const SkImageFilter*    fBackdrop;  // optional
+        SaveLayerFlags          fSaveLayerFlags;
     };
 
     int saveLayer(const SaveLayerRec&);
 
     /** This call balances a previous call to save(), and is used to remove all
         modifications to the matrix/clip/drawFilter state since the last save
         call.
         It is an error to call restore() more times than save() was called.
     */
     void restore();
@@ skipping 1129 matching lines @@
 
 class SkCanvasClipVisitor {
 public:
     virtual ~SkCanvasClipVisitor();
     virtual void clipRect(const SkRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipRRect(const SkRRect&, SkRegion::Op, bool antialias) = 0;
     virtual void clipPath(const SkPath&, SkRegion::Op, bool antialias) = 0;
 };
 
 #endif