[assembler] Introduce proper AssemblerBase::Print() for improved debuggability.

src/disassembler.cc

Index: src/disassembler.cc
diff --git a/src/disassembler.cc b/src/disassembler.cc
index b16f090e9d4bcc336923d61f5bc3dcb151ae3cc7..1158e01495968e581c64beab21f4aa7d8945fd0f 100644
--- a/src/disassembler.cc
+++ b/src/disassembler.cc
@@ -32,7 +32,9 @@ class V8NameConverter: public disasm::NameConverter {
 
 
 const char* V8NameConverter::NameOfAddress(byte* pc) const {
-  const char* name = code_->GetIsolate()->builtins()->Lookup(pc);
+  const char* name =
+      code_ == NULL ? NULL : code_->GetIsolate()->builtins()->Lookup(pc);
+
   if (name != NULL) {
     SNPrintF(v8_buffer_, "%s  (%p)", name, pc);
     return v8_buffer_.start();