add /img/n/m endpoint to skiaserve

include/private/GrAuditTrail.h

Index: include/private/GrAuditTrail.h
diff --git a/include/private/GrAuditTrail.h b/include/private/GrAuditTrail.h
index dab6fe73533171e69fb25398066a4b8ef291d116..e36c098bb6ff748a29b8406575beeca3cad205a8 100644
--- a/include/private/GrAuditTrail.h
+++ b/include/private/GrAuditTrail.h
@@ -114,6 +114,7 @@ public:
     };
 
     void getBoundsByClientID(SkTArray<BatchInfo>* outInfo, int clientID);
+    void getBoundsByBatchListID(BatchInfo* outInfo, int batchListID);
 
     void fullReset();
 
@@ -141,6 +142,8 @@ private:
     };
     typedef SkTArray<SkAutoTDelete<BatchNode>, true> BatchList;
 
+    void copyOutFromBatchList(BatchInfo* outBatchInfo, int batchListID);
+
     template <typename T>
     static void JsonifyTArray(SkString* json, const char* name, const T& array,
                               bool addComma);