Initial support for emitting unwinding information in perf jitdump.

src/arm64/assembler-arm64.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
@@ skipping 585 matching lines @@
   // Set up code descriptor.
   if (desc) {
     desc->buffer = reinterpret_cast<byte*>(buffer_);
     desc->buffer_size = buffer_size_;
     desc->instr_size = pc_offset();
     desc->reloc_size =
         static_cast<int>((reinterpret_cast<byte*>(buffer_) + buffer_size_) -
                          reloc_info_writer.pos());
     desc->origin = this;
     desc->constant_pool_size = 0;
+    desc->unwinding_info_size = 0;
+    desc->unwinding_info = nullptr;
   }
 }
 
 
 void Assembler::Align(int m) {
   DCHECK(m >= 4 && base::bits::IsPowerOfTwo32(m));
   while ((pc_offset() & (m - 1)) != 0) {
     nop();
   }
 }
@@ skipping 2597 matching lines @@
   movk(scratch, (target_offset >> 32) & 0xFFFF, 32);
   DCHECK((target_offset >> 48) == 0);
   add(rd, rd, scratch);
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_ARM64