[turbofan] Stage loop peeling.

We will try to loop inner-most loops if they have <1000 nodes (randomly chosen value).

This is an experimental CL to see the performance impact of peeling,
both on compile time and on the generated code.

Review-Url: https://codereview.chromium.org/2156573002
Cr-Commit-Position: refs/heads/master@{#37811}

src/flag-definitions.h

@@ -424,6 +424,7 @@ DEFINE_BOOL(omit_map_checks_for_leaf_maps, true,
 DEFINE_BOOL(turbo, false, "enable TurboFan compiler")
 DEFINE_IMPLICATION(turbo, turbo_asm_deoptimization)
 DEFINE_IMPLICATION(turbo, turbo_store_elimination)
+DEFINE_IMPLICATION(turbo, turbo_loop_peeling)
 DEFINE_BOOL(turbo_shipping, true, "enable TurboFan compiler on subset")
 DEFINE_BOOL(turbo_from_bytecode, false, "enable building graphs from bytecode")
 DEFINE_BOOL(turbo_sp_frame_access, false,