[compiler] Remove dangerous language mode accessors.

src/crankshaft/mips64/lithium-codegen-mips64.h

Index: src/crankshaft/mips64/lithium-codegen-mips64.h
diff --git a/src/crankshaft/mips64/lithium-codegen-mips64.h b/src/crankshaft/mips64/lithium-codegen-mips64.h
index 4a700bd66c0f973274d6f1b3f1c61476531adc92..9ac3192e3a058d06868b4cad61f971017a1a681a 100644
--- a/src/crankshaft/mips64/lithium-codegen-mips64.h
+++ b/src/crankshaft/mips64/lithium-codegen-mips64.h
@@ -136,8 +136,6 @@ class LCodeGen: public LCodeGenBase {
 #undef DECLARE_DO
 
  private:
-  LanguageMode language_mode() const { return info()->language_mode(); }
-
   Scope* scope() const { return scope_; }
 
   Register scratch0() { return kLithiumScratchReg; }