Add auto purging for SkPicture-related Ganesh resources (esp. layers)

This is intended to lower the bookkeeping burden for the Layer Caching feature. Cached layers are now automatically purged when a picture is deleted.

R=bsalomon@google.com

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/408923002

3 files changed, 11 insertions, 13 deletions

diff --git a/include/core/SkCanvas.h b/include/core/SkCanvas.h
index 6bd3cc5363..d68a9c50ab 100644
--- a/include/core/SkCanvas.h
+++ b/include/core/SkCanvas.h
@@ -964,12 +964,6 @@ public:
     */
     void EXPERIMENTAL_optimize(const SkPicture* picture);
 
-    /** PRIVATE / EXPERIMENTAL -- do not call
-        Purge all the discardable optimization information associated with
-        'picture'. If NULL is passed in, purge all discardable information.
-    */
-    void EXPERIMENTAL_purge(const SkPicture* picture);
-
     /** Draw the picture into this canvas. This method effective brackets the
         playback of the picture's draw calls with save/restore, so the state
         of this canvas will be unchanged after this call.
diff --git a/include/core/SkDevice.h b/include/core/SkDevice.h
index 2e06aab74f..4a9edee0ec 100644
--- a/include/core/SkDevice.h
+++ b/include/core/SkDevice.h
@@ -338,13 +338,6 @@ protected:
 
     /**
      *  PRIVATE / EXPERIMENTAL -- do not call
-     *  Purge all discardable optimization information for 'picture'. If
-     *  picture is NULL then purge discardable information for all pictures.
-     */
-    virtual void EXPERIMENTAL_purge(const SkPicture* picture);
-
-    /**
-     *  PRIVATE / EXPERIMENTAL -- do not call
      *  This entry point gives the backend an opportunity to take over the rendering
      *  of 'picture'. If optimization data is available (due to an earlier
      *  'optimize' call) this entry point should make use of it and return true
diff --git a/include/core/SkPicture.h b/include/core/SkPicture.h
index db996e02e8..21ebef32cd 100644
--- a/include/core/SkPicture.h
+++ b/include/core/SkPicture.h
@@ -190,6 +190,14 @@ public:
     bool suitableForGpuRasterization(GrContext*, const char ** = NULL) const;
 #endif
 
+    class DeletionListener : public SkRefCnt {
+    public:
+        virtual void onDeletion(uint32_t pictureID) = 0;
+    };
+
+    // Takes ref on listener.
+    void addDeletionListener(DeletionListener* listener) const;
+
 private:
     // V2 : adds SkPixelRef's generation ID.
     // V3 : PictInfo tag at beginning, and EOF tag at the end
@@ -237,7 +245,10 @@ private:
     int                   fWidth, fHeight;
     mutable SkAutoTUnref<const AccelData> fAccelData;
 
+    mutable SkTDArray<DeletionListener*> fDeletionListeners;  // pointers are refed
+
     void needsNewGenID() { fUniqueID = SK_InvalidGenID; }
+    void callDeletionListeners();
 
     // Create a new SkPicture from an existing SkPictureData. The new picture
     // takes ownership of 'data'.