Fix shadowed variable in gloo/gather.h

Summary:
Our upcoming compiler upgrade will require us not to have shadowed variables. Such variables have a _high_ bug rate and reduce readability, so we would like to avoid them even if the compiler was not forcing us to do so.

This codemod attempts to fix an instance of a shadowed variable. Please review with care: if it's failed the result will be a silent bug.

**What's a shadowed variable?**

Shadowed variables are variables in an inner scope with the same name as another variable in an outer scope. Having the same name for both variables might be semantically correct, but it can make the code confusing to read! It can also hide subtle bugs.

This diff fixes such an issue by renaming the variable.

 - If you approve of this diff, please use the "Accept & Ship" button :-)

Reviewed By: palmje

Differential Revision: D52582850

fbshipit-source-id: d285387f677b4e6800baf6cfed3df146b920d3b2

Author: r-barnes

gloo/gather.h

@@ -42,16 +42,16 @@ class GatherOptions {
     out = context->createUnboundBuffer(ptr, elements * sizeof(T));
   }
 
-  void setRoot(int root) {
-    this->root = root;
+  void setRoot(int root_2) {
+    this->root = root_2;
   }
 
-  void setTag(uint32_t tag) {
-    this->tag = tag;
+  void setTag(uint32_t tag_2) {
+    this->tag = tag_2;
   }
 
-  void setTimeout(std::chrono::milliseconds timeout) {
-    this->timeout = timeout;
+  void setTimeout(std::chrono::milliseconds timeout_2) {
+    this->timeout = timeout_2;
   }
 
  protected: