[heap] Do not invoke GC to make heap iterable.

src/debug/debug.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/debug/debug.h"
 
 #include "src/api.h"
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
@@ skipping 1301 matching lines @@
   // for which no JSFunction exists.
   {
     SharedFunctionInfo::Iterator iterator(isolate_);
     while (SharedFunctionInfo* shared = iterator.Next()) {
       if (!shared->OptimizedCodeMapIsCleared()) {
         shared->ClearOptimizedCodeMap();
       }
     }
   }
 
-  // Make sure we abort incremental marking.
-  isolate_->heap()->CollectAllGarbage(Heap::kMakeHeapIterableMask,
-                                      "prepare for break points");
-
   bool is_interpreted = shared->HasBytecodeArray();
 
   {
     // TODO(yangguo): with bytecode, we still walk the heap to find all
     // optimized code for the function to deoptimize. We can probably be
     // smarter here and avoid the heap walk.
     HeapIterator iterator(isolate_->heap());
     HeapObject* obj;
     bool include_generators = !is_interpreted && shared->is_generator();
 
@@ skipping 1250 matching lines @@
 }
 
 
 void LockingCommandMessageQueue::Clear() {
   base::LockGuard<base::Mutex> lock_guard(&mutex_);
   queue_.Clear();
 }
 
 }  // namespace internal
 }  // namespace v8