Fix compilation on x64 architectures

Contributed by Mathias Bynens <mathiasb@opera.com>.

BUG=v8:3110
LOG=Y
R=bmeurer@chromium.org, jarin@chromium.org

Review URL: https://codereview.chromium.org/143003007

Patch from Mathias Bynens <mathiasb@opera.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@18760 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/lithium-x64.h

@@ -1791,8 +1791,7 @@ class LCallWithDescriptor V8_FINAL : public LTemplateResultInstruction<1> {
   LCallWithDescriptor(const CallInterfaceDescriptor* descriptor,
                       ZoneList<LOperand*>& operands,
                       Zone* zone)
-    : descriptor_(descriptor),
-      inputs_(descriptor->environment_length() + 1, zone) {
+    : inputs_(descriptor->environment_length() + 1, zone) {
     ASSERT(descriptor->environment_length() + 1 == operands.length());
     inputs_.AddAll(operands, zone);
   }
@@ -1807,7 +1806,6 @@ class LCallWithDescriptor V8_FINAL : public LTemplateResultInstruction<1> {
 
   int arity() const { return hydrogen()->argument_count() - 1; }
 
-  const CallInterfaceDescriptor* descriptor_;
   ZoneList<LOperand*> inputs_;
 
   // Iterator support.