Add deferred texture upload API.

include/core/SkPixmap.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkPixmap_DEFINED
 #define SkPixmap_DEFINED
 
@@ skipping 193 matching lines @@
     /**
      *  Allocate memory for the pixels needed to match the specified Info and fill out the pixmap
      *  to point to that memory. The storage will be freed when this object is destroyed,
      *  or if another call to tryAlloc() or alloc() is made.
      *
      *  If the memory cannot be allocated, calls sk_throw().
      */
     void alloc(const SkImageInfo&);
 
     /**
+     * Gets the size and optionally the rowBytes that would be allocated by SkAutoPixmapStorage if
+     * alloc/tryAlloc was called.
+     */
+    static size_t AllocSize(const SkImageInfo& info, size_t* rowBytes);
+
+    /**
      *  Returns an SkData object wrapping the allocated pixels memory, and resets the pixmap.
      *  If the storage hasn't been allocated, the result is NULL.
      */
     const SkData* SK_WARN_UNUSED_RESULT detachPixelsAsData();
 
     // We wrap these so we can clear our internal storage
 
     void reset() {
         this->freeStorage();
         this->INHERITED::reset();
@@ skipping 64 matching lines @@
 private:
     void        (*fUnlockProc)(void*);
     void*       fUnlockContext;
     SkPixmap    fPixmap;
     bool        fIsLocked;
 
     friend class SkBitmap;
 };
 
 #endif