Add more instrumentation for Code::CopyFrom crasher.

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 8795 matching lines @@
     it.rinfo()->apply(delta);
   }
   CPU::FlushICache(instruction_start(), instruction_size());
 }
 
 
 void Code::CopyFrom(const CodeDesc& desc) {
   ASSERT(Marking::Color(this) == Marking::WHITE_OBJECT);
 
   // copy code
+  CHECK(IsCode());
+  CHECK(relocation_info()->IsByteArray());
+  CHECK(reinterpret_cast<intptr_t>(instruction_start()) ==
+        reinterpret_cast<intptr_t>(this) + Code::kHeaderSize - kHeapObjectTag);
   memmove(instruction_start(), desc.buffer, desc.instr_size);
 
   // copy reloc info
   // TODO(mstarzinger): Remove once we found the bug.
+  CHECK(IsCode());
   CHECK(relocation_info()->IsByteArray());
   memmove(relocation_start(),
           desc.buffer + desc.buffer_size - desc.reloc_size,
           desc.reloc_size);
 
   // unbox handles and relocate
   intptr_t delta = instruction_start() - desc.buffer;
   int mode_mask = RelocInfo::kCodeTargetMask |
                   RelocInfo::ModeMask(RelocInfo::EMBEDDED_OBJECT) |
                   RelocInfo::ModeMask(RelocInfo::GLOBAL_PROPERTY_CELL) |
@@ skipping 5498 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal