Lazy init batch unique ID

src/gpu/batches/GrBatch.h

Index: src/gpu/batches/GrBatch.h
diff --git a/src/gpu/batches/GrBatch.h b/src/gpu/batches/GrBatch.h
index b29c8a49b701ccccee3290233350f9ee1591877f..aae726eba95c4094462b3fa76e663100cc362b76 100644
--- a/src/gpu/batches/GrBatch.h
+++ b/src/gpu/batches/GrBatch.h
@@ -95,9 +95,13 @@ public:
 
     uint32_t classID() const { SkASSERT(kIllegalBatchID != fClassID); return fClassID; }
 
-#if GR_BATCH_SPEW
-    uint32_t uniqueID() const { return fUniqueID; }
-#endif
+    // We lazily initialize the uniqueID because currently the only user is GrAuditTrail
+    uint32_t uniqueID() const { 
+        if (kIllegalBatchID == fUniqueID) {
+            fUniqueID = GenBatchID();
+        }
+        return fUniqueID; 
+    }
     SkDEBUGCODE(bool isUsed() const { return fUsed; })
 
     /** Called prior to drawing. The batch should perform any resource creation necessary to
@@ -153,11 +157,9 @@ private:
 
     SkDEBUGCODE(bool                    fUsed;)
     const uint32_t                      fClassID;
-#if GR_BATCH_SPEW
     static uint32_t GenBatchID() { return GenID(&gCurrBatchUniqueID); }
-    const uint32_t                      fUniqueID;
+    mutable uint32_t                    fUniqueID;
     static int32_t                      gCurrBatchUniqueID;
-#endif
     static int32_t                      gCurrBatchClassID;
 };