[cpu-profiler] Include empty samples when context filter fails

If context filtration fails, ensure that we still include an empty
sample. This ensures that we can properly terminate stacks.

Bug: chromium:956688
Change-Id: I3edeb3434960c420e24827c209055f7c378361bf
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3058053Reviewed-by: Camillo Bruni <cbruni@chromium.org>
Commit-Queue: Andrew Comminos <acomminos@fb.com>
Cr-Commit-Position: refs/heads/master@{#75980}

src/profiler/profile-generator.cc

@@ -952,11 +952,13 @@ void CpuProfilesCollection::AddPathToCurrentProfiles(
   // method, we don't bother minimizing the duration of lock holding,
   // e.g. copying contents of the list to a local vector.
   current_profiles_semaphore_.Wait();
+  const ProfileStackTrace empty_path;
   for (const std::unique_ptr<CpuProfile>& profile : current_profiles_) {
-    if (profile->context_filter().Accept(native_context_address)) {
-      profile->AddPath(timestamp, path, src_line, update_stats,
-                       sampling_interval);
-    }
+    // If the context filter check failed, omit the contents of the stack.
+    bool accepts_context =
+        profile->context_filter().Accept(native_context_address);
+    profile->AddPath(timestamp, accepts_context ? path : empty_path, src_line,
+                     update_stats, sampling_interval);
   }
   current_profiles_semaphore_.Signal();
 }