Add an Android-framework-only stable ID to SkPixelRef.

src/core/SkPixelRef.cpp

Index: src/core/SkPixelRef.cpp
diff --git a/src/core/SkPixelRef.cpp b/src/core/SkPixelRef.cpp
index 0aa00e0bf58062fee2d3ddd7e706b81c18a44b0c..64075e5f525e9a6c7e5b31978b0433963cfc2f2e 100644
--- a/src/core/SkPixelRef.cpp
+++ b/src/core/SkPixelRef.cpp
@@ -203,6 +203,18 @@ uint32_t SkPixelRef::getGenerationID() const {
     return fGenerationID;
 }
 
+#ifdef SK_BUILD_FOR_ANDROID_FRAMEWORK
+uint32_t SkPixelRef::getStableID() const {
+    if (0 == fStableID) {
+        // Although it is okay for the stable ID to collide with a gen ID, it
+        // is also okay for them not to collide, and this allows us to share
+        // code.
+        fStableID = SkNextPixelRefGenerationID();
+    }
+    return fStableID;
+}
+#endif
+
 void SkPixelRef::addGenIDChangeListener(GenIDChangeListener* listener) {
     if (NULL == listener || !fUniqueGenerationID) {
         // No point in tracking this if we're not going to call it.