MIPS: Fix bad RegisterConfiguration usage in InstructionSequence unit tests.

test/unittests/compiler/register-allocator-unittest.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/pipeline.h"
 #include "test/unittests/compiler/instruction-sequence-unittest.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
@@ skipping 302 matching lines @@
 
   Allocate();
 }
 
 
 TEST_F(RegisterAllocatorTest, SpillPhi) {
   StartBlock();
   EndBlock(Branch(Imm(), 1, 2));
 
   StartBlock();
-  auto left = Define(Reg(0));
+  auto left = Define(Reg(GetAllocatableCode(0)));

[ivica.bogosavljevic, 2016/10/19 14:30:40]

I guess the same thing should be done everywhere. That's why I wanted to add
this code to the definition of InstructionSequenceTest::Reg, but that method is
static so it wasn't possible. 

   EndBlock(Jump(2));
 
   StartBlock();
-  auto right = Define(Reg(0));
+  auto right = Define(Reg(GetAllocatableCode(0)));
   EndBlock();
 
   StartBlock();
   auto phi = Phi(left, right);
   EmitCall(Slot(-1));
   Return(Reg(phi));
   EndBlock();
 
   Allocate();
 }
@@ skipping 450 matching lines @@
 INSTANTIATE_TEST_CASE_P(
     RegisterAllocatorTest, SlotConstraintTest,
     ::testing::Combine(::testing::ValuesIn(kParameterTypes),
                        ::testing::Range(0, SlotConstraintTest::kMaxVariant)));
 
 #endif  // GTEST_HAS_COMBINE
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8