Make peekPixels() usable with raster surface snapshots

src/image/SkImagePriv.h

Index: src/image/SkImagePriv.h
diff --git a/src/image/SkImagePriv.h b/src/image/SkImagePriv.h
index afaf3f173619ef376afaada9946345dcf4d1f1d8..876c4279b6ebaca031ad190a82b59dc41421f8f7 100644
--- a/src/image/SkImagePriv.h
+++ b/src/image/SkImagePriv.h
@@ -19,9 +19,15 @@ extern SkImage* SkNewImageFromPixelRef(const SkImageInfo&, SkPixelRef*,
 
 /**
  *  Examines the bitmap to decide if it can share the existing pixelRef, or
- *  if it needs to make a deep-copy of the pixels. The bitmap's pixelref will
- *  be shared if either the bitmap is marked as immutable, or canSharePixelRef
- *  is true.
+ *  if it needs to make a deep-copy of the pixels.
+ *
+ *  The bitmap's pixelref will be shared if either the bitmap is marked as
+ *  immutable, or forceSharePixelRef is true.  Shared pixel refs are also
+ *  locked when kLocked_SharedPixelRefMode is specified.
+ *
+ *  Passing kLocked_SharedPixelRefMode allows the image's peekPixels() method
+ *  to succeed, but it will force any lazy decodes/generators to execute if
+ *  they exist on the pixelref.
  *
  *  It is illegal to call this with a texture-backed bitmap.
  *
@@ -29,8 +35,12 @@ extern SkImage* SkNewImageFromPixelRef(const SkImageInfo&, SkPixelRef*,
  *  SkImageInfo, or the bitmap's pixels cannot be accessed, this will return
  *  NULL.
  */
+enum SharedPixelRefMode {
+    kLocked_SharedPixelRefMode,
+    kUnlocked_SharedPixelRefMode
+};
 extern SkImage* SkNewImageFromRasterBitmap(const SkBitmap&, bool forceSharePixelRef,
-                                           const SkSurfaceProps*);
+                                           const SkSurfaceProps*, SharedPixelRefMode);
 
 static inline size_t SkImageMinRowBytes(const SkImageInfo& info) {
     size_t minRB = info.minRowBytes();