Introduce locals to be read from a parcel ahead of time

so that error handling no longer crosses variable declarations.

Bug: 30570468
Change-Id: I365fec3cc33a8fdcd03a84bcbe05848ba290c475
diff --git a/AST.h b/AST.h
index da8f655..83c5d6d 100644
--- a/AST.h
+++ b/AST.h
@@ -97,6 +97,9 @@
     status_t generateStubSourceForMethod(
             Formatter &out, const Interface *iface, const Method *method) const;
 
+    void declareCppReaderLocals(
+            Formatter &out, const std::vector<TypedVar *> &arg) const;
+
     void emitCppReaderWriter(
             Formatter &out,
             const std::string &parcelObj,