Remove HCompareConstantEqAndBranch (never used), and its corresponding Lithium instructions.

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index 2a9ca324fc69561d7f4dafa2d76d7eb82fa93163..33aedbe2fa988fb9ff75a8fe1e3cdb7893b20434 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -2240,13 +2240,6 @@ void LCodeGen::DoCmpObjectEqAndBranch(LCmpObjectEqAndBranch* instr) {
 }
 
 
-void LCodeGen::DoCmpConstantEqAndBranch(LCmpConstantEqAndBranch* instr) {
-  Register left = ToRegister(instr->left());
-
-  EmitBranch(instr, eq, left, Operand(instr->hydrogen()->right()));
-}
-
-
 Condition LCodeGen::EmitIsObject(Register input,
                                  Register temp1,
                                  Register temp2,