Treat weak references in context weakly in write barrier.

src/objects-inl.h

 // 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 1257 matching lines @@
       reinterpret_cast<base::AtomicWord*>(FIELD_ADDR(p, offset)), \
       reinterpret_cast<base::AtomicWord>(value));
 
 #define WRITE_BARRIER(heap, object, offset, value)                      \
   heap->incremental_marking()->RecordWrite(                             \
       object, HeapObject::RawField(object, offset), value);             \
   if (heap->InNewSpace(value)) {                                        \
     heap->RecordWrite(object->address(), offset);                       \
   }
 
-#define CONDITIONAL_WRITE_BARRIER(heap, object, offset, value, mode)    \
-  if (mode == UPDATE_WRITE_BARRIER) {                                   \
-    heap->incremental_marking()->RecordWrite(                           \
-      object, HeapObject::RawField(object, offset), value);             \
-    if (heap->InNewSpace(value)) {                                      \
-      heap->RecordWrite(object->address(), offset);                     \
-    }                                                                   \
+#define CONDITIONAL_WRITE_BARRIER(heap, object, offset, value, mode) \
+  if (mode != SKIP_WRITE_BARRIER) {                                  \
+    if (mode == UPDATE_WRITE_BARRIER) {                              \
+      heap->incremental_marking()->RecordWrite(                      \
+          object, HeapObject::RawField(object, offset), value);      \
+    }                                                                \
+    if (heap->InNewSpace(value)) {                                   \
+      heap->RecordWrite(object->address(), offset);                  \
+    }                                                                \
   }
 
 #ifndef V8_TARGET_ARCH_MIPS
   #define READ_DOUBLE_FIELD(p, offset) \
     (*reinterpret_cast<const double*>(FIELD_ADDR_CONST(p, offset)))
 #else  // V8_TARGET_ARCH_MIPS
   // Prevent gcc from using load-double (mips ldc1) on (possibly)
   // non-64-bit aligned HeapNumber::value.
   static inline double read_double_field(const void* p, int offset) {
     union conversion {
@@ skipping 6346 matching lines @@
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_