Revert "Revert of Use the GrCacheable ID to eliminate the need for notifications to GrGpuGL when textures and RTs areā€¦ (https://codereview.chromium.org/376703009/)"

This reverts commit 249171e7d29b5559f3eefe9dbd437030bfad3fda.

Uses 32 bit id instead of 64. Renamed instanceID to uniqueID to match existing code.

R=robertphillips@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/414493002
diff --git a/include/core/SkTypes.h b/include/core/SkTypes.h
index 5ff57f8..e264f48 100644
--- a/include/core/SkTypes.h
+++ b/include/core/SkTypes.h
@@ -325,6 +325,9 @@
 /** The generation IDs in Skia reserve 0 has an invalid marker.
  */
 #define SK_InvalidGenID     0
+/** The unique IDs in Skia reserve 0 has an invalid marker.
+ */
+#define SK_InvalidUniqueID  0
 
 /****************************************************************************
     The rest of these only build with C++