[csa] disable CSA re-scheduling

Disable CSA re-scheduling for the branch point, to address performance
regressions.

Bug: chromium:907011
Change-Id: I608ae23c20d8e1dd9a233dcb2d3f4ab4d8a5241e
Reviewed-on: https://chromium-review.googlesource.com/c/1351009Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57930}

src/flag-definitions.h

@@ -437,7 +437,7 @@ DEFINE_BOOL(trace_verify_csa, false, "trace code stubs verification")
 DEFINE_STRING(csa_trap_on_node, nullptr,
               "trigger break point when a node with given id is created in "
               "given stub. The format is: StubName,NodeId")
-DEFINE_BOOL_READONLY(optimize_csa, true,
+DEFINE_BOOL_READONLY(optimize_csa, false,
                      "run the optimizing Turbofan backend in the CSA pipeline")
 DEFINE_NEG_IMPLICATION(optimize_csa, turbo_rewrite_far_jumps)
 DEFINE_BOOL_READONLY(fixed_array_bounds_checks, DEBUG_BOOL,