Unflake and speedup JsNative*Sample cpu profile tests

src/profile-generator.cc

Index: src/profile-generator.cc
diff --git a/src/profile-generator.cc b/src/profile-generator.cc
index 945bdd6cc12f5ea883ea6a30a12c24f938b81de2..44f7555b350cfeff8f078ac0da75fa75f09547fd 100644
--- a/src/profile-generator.cc
+++ b/src/profile-generator.cc
@@ -469,9 +469,10 @@ bool CpuProfilesCollection::StartProfiling(const char* title,
   }
   for (int i = 0; i < current_profiles_.length(); ++i) {
     if (strcmp(current_profiles_[i]->title(), title) == 0) {
-      // Ignore attempts to start profile with the same title.
+      // Ignore attempts to start profile with the same title...
       current_profiles_semaphore_.Signal();
-      return false;
+      // ... though return true to force it collect a sample.
+      return true;
     }
   }
   current_profiles_.Add(new CpuProfile(title, record_samples));