MIPS: small test-case fix for chaining of fixup position.

test/cctest/test-assembler-mips.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
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 // modification, are permitted provided that the following conditions are
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 //
 //     * Redistributions of source code must retain the above copyright
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@@ skipping 1250 matching lines @@
 
 
 TEST(MIPS15) {
   // Test chaining of label usages within instructions (issue 1644).
   InitializeVM();
   v8::HandleScope scope;
   Assembler assm(Isolate::Current(), NULL, 0);
 
   Label target;
   __ beq(v0, v1, &target);
+  __ nop();
   __ bne(v0, v1, &target);
+  __ nop();
   __ bind(&target);
   __ nop();
 }
 
 #undef __