Narrow the scope of writable code to the forwarding phase of become instead of the whole isolate re…

runtime/vm/isolate_reload.cc

 // Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/isolate_reload.h"
 
 #include "vm/become.h"
 #include "vm/bit_vector.h"
 #include "vm/code_generator.h"
 #include "vm/compiler.h"
@@ skipping 445 matching lines @@
       HashTables::New<UnorderedHashMap<LibraryMapTraits> >(4);
   become_map_storage_ =
       HashTables::New<UnorderedHashMap<BecomeMapTraits> >(4);
   // Keep a separate array for enum mappings to avoid having to invoke
   // hashCode on the instances.
   become_enum_mappings_ = GrowableObjectArray::New(Heap::kOld);
 
   // Disable the background compiler while we are performing the reload.
   BackgroundCompiler::Disable();
 
-  if (FLAG_write_protect_code) {
-    // Disable code page write protection while we are reloading.
-    I->heap()->WriteProtectCode(false);
-  }
-
   // Ensure all functions on the stack have unoptimized code.
   EnsuredUnoptimizedCodeForStack();
   // Deoptimize all code that had optimizing decisions that are dependent on
   // assumptions from field guards or CHA or deferred library prefixes.
   // TODO(johnmccutchan): Deoptimizing dependent code here (before the reload)
   // is paranoid. This likely can be moved to the commit phase.
   DeoptimizeDependentCode();
   Checkpoint();
 
   Object& result = Object::Handle(thread->zone());
@@ skipping 53 matching lines @@
     isolate()->set_last_reload_timestamp(reload_timestamp_);
   } else {
     ReportReasonsForCancelling();
     Rollback();
   }
   // ValidateReload mutates the direct subclass information and does
   // not remove dead subclasses.  Rebuild the direct subclass
   // information from scratch.
   RebuildDirectSubclasses();
 
-  if (FLAG_write_protect_code) {
-    // Re-enable code page write protection.
-    I->heap()->WriteProtectCode(true);
-  }
-
   BackgroundCompiler::Enable();
 
   reload_aborted_ = HasReasonsForCancelling();
   ReportOnJSON(js_);
 }
 
 
 void IsolateReloadContext::ReportOnJSON(JSONStream* stream) {
   JSONObject jsobj(stream);
   jsobj.AddProperty("type", "ReloadReport");
@@ skipping 1043 matching lines @@
         ASSERT(!super_cls.IsNull());
         super_cls.AddDirectSubclass(cls);
       }
     }
   }
 }
 
 #endif  // !PRODUCT
 
 }  // namespace dart