[profiler] Delete unused NodesPair

Cleanup, delete unused struct.

Bug: 
Change-Id: I4ea5e81d6d0711d7cf3fdd279f8b0d136bcd6db3
Reviewed-on: https://chromium-review.googlesource.com/846760
Commit-Queue: Michael Stanton <mvstanton@chromium.org>
Reviewed-by: Michael Stanton <mvstanton@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50319}

src/profiler/profile-generator.cc

@@ -332,14 +332,6 @@ ProfileNode* ProfileTree::AddPathFromEnd(const std::vector<CodeEntry*>& path,
 }
 
 
-struct NodesPair {
-  NodesPair(ProfileNode* src, ProfileNode* dst)
-      : src(src), dst(dst) { }
-  ProfileNode* src;
-  ProfileNode* dst;
-};
-
-
 class Position {
  public:
   explicit Position(ProfileNode* node)