Backport hash collision workaround to 3.6.

src/mips/macro-assembler-mips.h

 // Copyright 2011 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 653 matching lines @@
                             Register scratch,
                             Label* fail);
 
 #ifdef ENABLE_DEBUGGER_SUPPORT
   // -------------------------------------------------------------------------
   // Debugger Support.
 
   void DebugBreak();
 #endif
 
+  void InitializeRootRegister() {
+    ExternalReference roots_address =
+        ExternalReference::roots_address(isolate());
+    li(kRootRegister, Operand(roots_address));
+  }
 
   // -------------------------------------------------------------------------
   // Exception handling.
 
   // Push a new try handler and link into try handler chain.
   // The return address must be passed in register ra.
   // Clobber t0, t1, t2.
   void PushTryHandler(CodeLocation try_location, HandlerType type);
 
   // Unlink the stack handler on top of the stack from the try handler chain.
@@ skipping 541 matching lines @@
 #define CODE_COVERAGE_TOSTRING(x) CODE_COVERAGE_STRINGIFY(x)
 #define __FILE_LINE__ __FILE__ ":" CODE_COVERAGE_TOSTRING(__LINE__)
 #define ACCESS_MASM(masm) masm->stop(__FILE_LINE__); masm->
 #else
 #define ACCESS_MASM(masm) masm->
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_MIPS_MACRO_ASSEMBLER_MIPS_H_