leave pixel memory uninitialized for opaque alpha type in SkSurface::MakeRaster

include/core/SkSurface.h

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkSurface_DEFINED
 #define SkSurface_DEFINED
 
@@ skipping 33 matching lines @@
 
     /**
      *  The same as NewRasterDirect, but also accepts a call-back routine, which is invoked
      *  when the surface is deleted, and is passed the pixel memory and the specified context.
      */
     static sk_sp<SkSurface> MakeRasterDirectReleaseProc(const SkImageInfo&, void* pixels, size_t rowBytes,
                                                  void (*releaseProc)(void* pixels, void* context),
                                                  void* context, const SkSurfaceProps* = nullptr);
 
     /**
-     *  Return a new surface, with the memory for the pixels automatically allocated and
-     *  zero-initialized, but respecting the specified rowBytes. If rowBytes==0, then a default
-     *  value will be chosen. If a non-zero rowBytes is specified, then any images snapped off of
-     *  this surface (via makeImageSnapshot()) are guaranteed to have the same rowBytes.
+     *  Return a new surface, with the memory for the pixels automatically allocated but respecting
+     *  the specified rowBytes. If rowBytes==0, then a default value will be chosen. If a non-zero
+     *  rowBytes is specified, then any images snapped off of this surface (via makeImageSnapshot())
+     *  are guaranteed to have the same rowBytes.
+     *
+     *  If the requested alpha type is not opaque, then the surface's pixel memory will be
+     *  zero-initialized. If it is opaque, then it will be left uninitialized, and the caller is
+     *  responsible for initially clearing the surface.
      *
      *  If the requested surface cannot be created, or the request is not a
      *  supported configuration, NULL will be returned.
      */
     static sk_sp<SkSurface> MakeRaster(const SkImageInfo&, size_t rowBytes, const SkSurfaceProps*);
 
     /**
      *  Allocate a new surface, automatically computing the rowBytes.
      */
     static sk_sp<SkSurface> MakeRaster(const SkImageInfo& info,
@@ skipping 321 matching lines @@
 private:
     const SkSurfaceProps fProps;
     const int            fWidth;
     const int            fHeight;
     uint32_t             fGenerationID;
 
     typedef SkRefCnt INHERITED;
 };
 
 #endif