Use register allocator for context on x64.

test/cctest/test-code-stubs-ia32.cc

Index: test/cctest/test-code-stubs-ia32.cc
diff --git a/test/cctest/test-code-stubs-ia32.cc b/test/cctest/test-code-stubs-ia32.cc
index 3f621758e3c0e5f9c0955cd1f15deaf2c21eb94d..34db99fbae5582b85318e865d84a2984b6d92407 100644
--- a/test/cctest/test-code-stubs-ia32.cc
+++ b/test/cctest/test-code-stubs-ia32.cc
@@ -73,7 +73,7 @@ ConvertDToIFunc MakeConvertDToIFuncTrampoline(Isolate* isolate,
   // Save registers make sure they don't get clobbered.
   int reg_num = 0;
   for (;reg_num < Register::NumAllocatableRegisters(); ++reg_num) {
-    Register reg = Register::from_code(reg_num);
+    Register reg = Register::FromAllocationIndex(reg_num);
     if (!reg.is(esp) && !reg.is(ebp) && !reg.is(destination_reg)) {
       __ push(reg);
       param_offset += kPointerSize;
@@ -91,7 +91,7 @@ ConvertDToIFunc MakeConvertDToIFuncTrampoline(Isolate* isolate,
 
   // Make sure no registers have been unexpectedly clobbered
   for (--reg_num; reg_num >= 0; --reg_num) {
-    Register reg = Register::from_code(reg_num);
+    Register reg = Register::FromAllocationIndex(reg_num);
     if (!reg.is(esp) && !reg.is(ebp) && !reg.is(destination_reg)) {
       __ cmp(reg, MemOperand(esp, 0));
       __ Assert(equal, kRegisterWasClobbered);