Revert "[snapshot] Fix clearing of feedback vector in serializer (follow-up 2)"

This reverts commit 1320c917.

Reason for revert: The code in SFI is also flushed by the serializer with FunctionCodeHandling::kClear, so this fix does not work with --no_flush_bytecode.

Original change's description:
> [snapshot] Fix clearing of feedback vector in serializer (follow-up 2)
> 
> Bug: v8:7857
> Change-Id: I3940ae2830adb6c572e079551b7bba7d84462afd
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1715444
> Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#62881}

TBR=ulan@chromium.org,rmcilroy@chromium.org,yangguo@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: v8:7857
Change-Id: If85fe29b2cdf6523ee53895628da38d942d45c2b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1719190Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#62935}

src/api/api.cc

@@ -811,10 +811,15 @@ StartupData SnapshotCreator::CreateBlob(
       // Complete in-object slack tracking for all functions.
       fun.CompleteInobjectSlackTrackingIfActive();
 
-      fun.ResetIfBytecodeFlushed();
-
       // Also, clear out feedback vectors, or any optimized code.
-      if (fun.IsOptimized() || fun.IsInterpreted()) {
+      // Note that checking for fun.IsOptimized() || fun.IsInterpreted() is not
+      // sufficient because the function can have a feedback vector even if it
+      // is not compiled (e.g. when the bytecode was flushed). On the other
+      // hand, only checking for the feedback vector is not sufficient because
+      // there can be multiple functions sharing the same feedback vector. So we
+      // need all these checks.
+      if (fun.IsOptimized() || fun.IsInterpreted() ||
+          !fun.raw_feedback_cell().value().IsUndefined()) {
         fun.raw_feedback_cell().set_value(
             i::ReadOnlyRoots(isolate).undefined_value());
         fun.set_code(isolate->builtins()->builtin(i::Builtins::kCompileLazy));