[turbofan] Introduce --min-inlining-frequency flag.

src/compiler/js-inlining-heuristic.cc

Index: src/compiler/js-inlining-heuristic.cc
diff --git a/src/compiler/js-inlining-heuristic.cc b/src/compiler/js-inlining-heuristic.cc
index 9774de28e5f23911e4e1ac1950ce63060fbe73e4..abff7b6571d37d8b3505a7e149d84ddbf6ac4a2b 100644
--- a/src/compiler/js-inlining-heuristic.cc
+++ b/src/compiler/js-inlining-heuristic.cc
@@ -146,6 +146,13 @@ Reduction JSInliningHeuristic::Reduce(Node* node) {
       break;
   }
 
+  // Don't consider a {candidate} whose frequency is below the
+  // threshold, i.e. a call site that is only hit once every N
+  // invocations of the caller.
+  if (candidate.frequency < FLAG_min_inlining_frequency) {
+    return NoChange();
+  }
+
   // In the general case we remember the candidate for later.
   candidates_.insert(candidate);
   return NoChange();