Allow client to force an SkImage snapshot to be unique (and uniquely own its backing store).

src/image/SkSurface.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 "SkSurface_Base.h"
 #include "SkImagePriv.h"
 #include "SkCanvas.h"
@@ skipping 146 matching lines @@
 
 void SkSurface::notifyContentWillChange(ContentChangeMode mode) {
     asSB(this)->aboutToDraw(mode);
 }
 
 SkCanvas* SkSurface::getCanvas() {
     return asSB(this)->getCachedCanvas();
 }
 
 SkImage* SkSurface::newImageSnapshot(Budgeted budgeted) {
-    SkImage* image = asSB(this)->getCachedImage(budgeted);
-    SkSafeRef(image);   // the caller will call unref() to balance this
-    return image;
+    // the caller will call unref() to balance this
+    return asSB(this)->refCachedImage(budgeted, kNo_ForceUnique);
+}
+
+SkImage* SkSurface::newImageSnapshot(Budgeted budgeted, ForceUnique unique) {
+    // the caller will call unref() to balance this
+    return asSB(this)->refCachedImage(budgeted, unique);
 }
 
 SkSurface* SkSurface::newSurface(const SkImageInfo& info) {
     return asSB(this)->onNewSurface(info);
 }
 
 void SkSurface::draw(SkCanvas* canvas, SkScalar x, SkScalar y,
                      const SkPaint* paint) {
     return asSB(this)->onDraw(canvas, x, y, paint);
 }
@@ skipping 32 matching lines @@
                                              const SkSurfaceProps*) {
     return nullptr;
 }
 
 SkSurface* SkSurface::NewFromBackendRenderTarget(GrContext*, const GrBackendRenderTargetDesc&,
                                                  const SkSurfaceProps*) {
     return nullptr;
 }
 
 #endif