cache private readback for gpu-images

src/image/SkImage_Gpu.h

Index: src/image/SkImage_Gpu.h
diff --git a/src/image/SkImage_Gpu.h b/src/image/SkImage_Gpu.h
index 4c7ebd6f7185aef5c4d36c5157ba18982c48943f..9481690714c9619b6b17369b549f6c1b580f21c5 100644
--- a/src/image/SkImage_Gpu.h
+++ b/src/image/SkImage_Gpu.h
@@ -8,6 +8,7 @@
 #ifndef SkImage_Gpu_DEFINED
 #define SkImage_Gpu_DEFINED
 
+#include "SkAtomics.h"
 #include "GrTexture.h"
 #include "GrGpuResourcePriv.h"
 #include "SkBitmap.h"
@@ -17,14 +18,13 @@
 
 class SkImage_Gpu : public SkImage_Base {
 public:
-    
-
     /**
      *  An "image" can be a subset/window into a larger texture, so we explicit take the
      *  width and height.
      */
     SkImage_Gpu(int w, int h, uint32_t uniqueID, SkAlphaType, GrTexture*,
                 int sampleCountForNewSurfaces, SkSurface::Budgeted);
+    ~SkImage_Gpu() override;
 
     void applyBudgetDecision() const {
         GrTexture* tex = this->getTexture();
@@ -47,10 +47,12 @@ public:
                       int srcX, int srcY) const override;
 
 private:
-    SkAutoTUnref<GrTexture> fTexture;
-    const int               fSampleCountForNewSurfaces;   // 0 if we don't know
-    const SkAlphaType       fAlphaType;
-    SkSurface::Budgeted     fBudgeted;
+    SkAutoTUnref<GrTexture>     fTexture;
+    const int                   fSampleCountForNewSurfaces;   // 0 if we don't know
+    const SkAlphaType           fAlphaType;
+    const SkSurface::Budgeted   fBudgeted;
+    mutable SkAtomic<bool>      fAddedRasterVersionToCache;
+
 
     typedef SkImage_Base INHERITED;
 };