ART: Add thread offset printing hook to disassembler

To prepare separation of disassembler from libart, add a function
hook to the disassembler options for thread offset name printing.

Bug: 15436106
Change-Id: I9e9b7e565ae923952c64026f675ac527b560f51b
diff --git a/disassembler/disassembler_mips.h b/disassembler/disassembler_mips.h
index b0e49b3..6342f22 100644
--- a/disassembler/disassembler_mips.h
+++ b/disassembler/disassembler_mips.h
@@ -26,9 +26,8 @@
 
 class DisassemblerMips FINAL : public Disassembler {
  public:
-  DisassemblerMips(DisassemblerOptions* options, bool is64bit)
+  explicit DisassemblerMips(DisassemblerOptions* options)
       : Disassembler(options),
-        is64bit_(is64bit),
         last_ptr_(nullptr),
         last_instr_(0) {}
 
@@ -36,8 +35,6 @@
   void Dump(std::ostream& os, const uint8_t* begin, const uint8_t* end) OVERRIDE;
 
  private:
-  const bool is64bit_;
-
   // Address and encoding of the last disassembled instruction.
   // Needed to produce more readable disassembly of certain 2-instruction sequences.
   const uint8_t* last_ptr_;