[compiler] Put shared function marking behind a flag

src/compiler.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler.h"
 
 #include <algorithm>
 #include <memory>
 
 #include "src/asmjs/asm-js.h"
@@ skipping 960 matching lines @@
     if (FLAG_trace_opt) {
       PrintF("[found optimized code for ");
       function->ShortPrint();
       PrintF(" during unoptimized compile]\n");
     }
     DCHECK(function->shared()->is_compiled());
     return cached_code;
   }
 
   if (function->shared()->was_marked_for_optimization()) {
+    DCHECK(FLAG_optimize_shared_functions);
+
     function->shared()->set_was_marked_for_optimization(false);
 
     if (FLAG_trace_opt) {
       PrintF("[optimizing function ");
       function->PrintName();
       PrintF(" eagerly because shared function was previously marked]\n");
     }
 
     Handle<Code> opt_code;
     if (GetOptimizedCode(function, Compiler::NOT_CONCURRENT)
@@ skipping 837 matching lines @@
     DCHECK(shared->is_compiled());
     function->set_literals(cached.literals);
   } else if (shared->is_compiled()) {
     // TODO(mvstanton): pass pretenure flag to EnsureLiterals.
     JSFunction::EnsureLiterals(function);
   }
 }
 
 }  // namespace internal
 }  // namespace v8