Add snapshot entry point to SkPictureRecorder

include/core/SkPictureRecorder.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPictureRecorder_DEFINED
 #define SkPictureRecorder_DEFINED
 
@@ skipping 64 matching lines @@
         ref which the caller must take ownership of.
     */
     SkPicture* endRecording() {
         if (NULL != fPicture.get()) {
             fPicture->endRecording();
             return fPicture.detach();
         }
         return NULL;
     }
 
+    /** Create an intermediate SkPicture of the in-progress recording.
+        Future recorded operations will not appear in the snapshot. If no
+        recording is in progress this will return NULL. 
+    */
+    SkPicture* snapshot() {
+        if (NULL != fPicture) {
+            return SkNEW_ARGS(SkPicture, (*fPicture));

[scroggo, 2014/04/25 14:16:52]

I haven't followed along with all the picture changes. Will this allow the
caller to continue recording after they've made the snapshot?

[robertphillips, 2014/04/25 14:55:28]

Currently - yes. I believe the desire is to not assume the burden of carrying
such a capability going forward.

[scroggo, 2014/04/25 15:00:44]

When that day comes, what will the Android approach be? Deprecate the Picture
copy constructor?

Could we have a function in picture recorder that copies the picture recorder?
Or is that a price we don't want to pay?

+        }
+
+        return NULL;
+    }
+
     /** Enable/disable all the picture recording optimizations (i.e.,
         those in SkPictureRecord). It is mainly intended for testing the
         existing optimizations (i.e., to actually have the pattern
         appear in an .skp we have to disable the optimization). Call right
         after 'beginRecording'.
     */
     void internalOnly_EnableOpts(bool enableOpts) {
         if (NULL != fPicture.get()) {
             fPicture->internalOnly_EnableOpts(enableOpts);
         }
     }
 
 private:
 #ifdef SK_SUPPORT_LEGACY_DERIVED_PICTURE_CLASSES
     SkAutoTUnref<SkPictureFactory>  fFactory;
 #endif
 
     SkAutoTUnref<SkPicture>         fPicture;
 
     typedef SkNoncopyable INHERITED;
 };
 
 #endif