[turbofan] Factor C call descriptor building into compiler/c-linkage.cc.

src/compiler/x87/linkage-x87.cc

Index: src/compiler/x87/linkage-x87.cc
diff --git a/src/compiler/x87/linkage-x87.cc b/src/compiler/x87/linkage-x87.cc
index 37bfd6d9e6300c4f26029a3a38ecd260b353062c..1d20006cdea0e18b5b6761ca87eb7b58c6f1f59d 100644
--- a/src/compiler/x87/linkage-x87.cc
+++ b/src/compiler/x87/linkage-x87.cc
@@ -21,13 +21,6 @@ struct X87LinkageHelperTraits {
   static Register InterpreterDispatchTableReg() { return ebx; }
   static Register RuntimeCallFunctionReg() { return ebx; }
   static Register RuntimeCallArgCountReg() { return eax; }
-  static RegList CCalleeSaveRegisters() {
-    return esi.bit() | edi.bit() | ebx.bit();
-  }
-  static RegList CCalleeSaveFPRegisters() { return 0; }
-  static Register CRegisterParameter(int i) { return no_reg; }
-  static int CRegisterParametersLength() { return 0; }
-  static int CStackBackingStoreLength() { return 0; }
 };
 
 typedef LinkageHelper<X87LinkageHelperTraits> LH;
@@ -57,12 +50,6 @@ CallDescriptor* Linkage::GetStubCallDescriptor(
 }
 
 
-CallDescriptor* Linkage::GetSimplifiedCDescriptor(Zone* zone,
-                                                  const MachineSignature* sig) {
-  return LH::GetSimplifiedCDescriptor(zone, sig);
-}
-
-
 CallDescriptor* Linkage::GetInterpreterDispatchDescriptor(Zone* zone) {
   return LH::GetInterpreterDispatchDescriptor(zone);
 }