[runtime] Remove the redundant %_IsObject intrinsic.

src/mips64/lithium-codegen-mips64.h

Index: src/mips64/lithium-codegen-mips64.h
diff --git a/src/mips64/lithium-codegen-mips64.h b/src/mips64/lithium-codegen-mips64.h
index 420111b3cabb3fd0590ef857ad635a9b99d9cd4b..b08de167bea9ec8db80c0314d50644969d801298 100644
--- a/src/mips64/lithium-codegen-mips64.h
+++ b/src/mips64/lithium-codegen-mips64.h
@@ -305,15 +305,6 @@ class LCodeGen: public LCodeGenBase {
                          Register* cmp1,
                          Operand* cmp2);
 
-  // Emits optimized code for %_IsObject(x).  Preserves input register.
-  // Returns the condition on which a final split to
-  // true and false label should be made, to optimize fallthrough.
-  Condition EmitIsObject(Register input,
-                         Register temp1,
-                         Register temp2,
-                         Label* is_not_object,
-                         Label* is_object);
-
   // Emits optimized code for %_IsString(x).  Preserves input register.
   // Returns the condition on which a final split to
   // true and false label should be made, to optimize fallthrough.