Don't create ScopeInfo if there already is one.

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 496 matching lines @@
       !GenerateUnoptimizedCode(info)) {
     Isolate* isolate = info->isolate();
     if (!isolate->has_pending_exception()) isolate->StackOverflow();
     return false;
   }
   return true;
 }
 
 void InstallSharedScopeInfo(CompilationInfo* info,
                             Handle<SharedFunctionInfo> shared) {
-  Handle<ScopeInfo> scope_info =
-      ScopeInfo::Create(info->isolate(), info->zone(), info->scope());
+  Handle<ScopeInfo> scope_info = info->scope()->GetScopeInfo(info->isolate());
   shared->set_scope_info(*scope_info);
 }
 
 void InstallSharedCompilationResult(CompilationInfo* info,
                                     Handle<SharedFunctionInfo> shared) {
   // TODO(mstarzinger): Compiling for debug code might be used to reveal inner
   // functions via {FindSharedFunctionInfoInScript}, in which case we end up
   // regenerating existing bytecode. Fix this!
   if (info->is_debug() && info->has_bytecode_array()) {
     shared->ClearBytecodeArray();
@@ skipping 1435 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