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

src/flag-definitions.h

Index: src/flag-definitions.h
diff --git a/src/flag-definitions.h b/src/flag-definitions.h
index 513f81a91df654cef80e6c0554ebdf4273856cb5..4c20e8fb1b45e30b5c6c7c34bb8d86a7d4806584 100644
--- a/src/flag-definitions.h
+++ b/src/flag-definitions.h
@@ -361,6 +361,7 @@ DEFINE_INT(max_inlined_nodes, 200,
            "maximum number of AST nodes considered for a single inlining")
 DEFINE_INT(max_inlined_nodes_cumulative, 400,
            "maximum cumulative number of AST nodes considered for inlining")
+DEFINE_FLOAT(min_inlining_frequency, 0.15, "minimum frequency for inlining")
 DEFINE_BOOL(loop_invariant_code_motion, true, "loop invariant code motion")
 DEFINE_BOOL(fast_math, true, "faster (but maybe less accurate) math functions")
 DEFINE_BOOL(hydrogen_stats, false, "print statistics for hydrogen")