protobuf: Fix sizeof for long fields

A typo had us using the wrong method name.

Change-Id: If67b526639628e5a6bcb90ffcace84428c28a92f
Signed-off-by: Shawn O. Pearce <sop@google.com>
diff --git a/src/main/java/com/google/gwtorm/protobuf/CodecGen.java b/src/main/java/com/google/gwtorm/protobuf/CodecGen.java
index e8598ae..a7ab7ef 100644
--- a/src/main/java/com/google/gwtorm/protobuf/CodecGen.java
+++ b/src/main/java/com/google/gwtorm/protobuf/CodecGen.java
@@ -454,7 +454,7 @@
         cgs.preinc();
         cgs.push(f.getColumnID());
         cgs.pushFieldValue();
-        cgs.doinc("computeSInt64", Type.INT_TYPE, Type.LONG_TYPE);
+        cgs.doinc("computeSInt64Size", Type.INT_TYPE, Type.LONG_TYPE);
         break;
 
       case Type.ARRAY: