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/Interface.cpp b/Interface.cpp
index 42186af..2c65865 100644
--- a/Interface.cpp
+++ b/Interface.cpp
@@ -62,6 +62,9 @@
         parcelObj + (parcelObjIsPointer ? "->" : ".");
 
     if (isReader) {
+        out << "{\n";
+        out.indent();
+
         const std::string binderName = "_hidl_" + name + "_binder";
 
         out << "::android::sp<::android::hardware::IBinder> "
@@ -81,6 +84,9 @@
             << "::asInterface("
             << binderName
             << ");\n";
+
+        out.unindent();
+        out << "}\n\n";
     } else {
         out << "_hidl_err = ";
         out << parcelObjDeref