unify pixelref and image ID space, so we can share IDs when we share pixels

include/core/SkImage.h

Index: include/core/SkImage.h
diff --git a/include/core/SkImage.h b/include/core/SkImage.h
index 2b759b800387882577b6cad8a7c029b44b56a373..ea4855ec9a8fd59e4fb037a672332160cdebe74b 100644
--- a/include/core/SkImage.h
+++ b/include/core/SkImage.h
@@ -283,10 +283,10 @@ public:
     bool asLegacyBitmap(SkBitmap*, LegacyBitmapMode) const;
     
 protected:
-    SkImage(int width, int height) :
+    SkImage(int width, int height, uint32_t uniqueID) :
         fWidth(width),
         fHeight(height),
-        fUniqueID(NextUniqueID()) {
+        fUniqueID(uniqueID ? uniqueID : NextUniqueID()) {

[f(malita), 2015/07/30 20:24:26]

Nit: since we're using a constant in subclases (kNeedNewImageUniqueID), it seems
a bit odd to compare directly with 0 here.  Can you push the test down into
SkImage_Base() where the constant is visible?

[reed1, 2015/07/30 21:17:08]

Problem: that symbol is in a private header
Solution: move the constructor into .cpp

 
         SkASSERT(width > 0);
         SkASSERT(height > 0);