Compile fix for older GCCs.

TBR=titzer@chromium.org

Review URL: https://codereview.chromium.org/21142007

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@15981 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/hydrogen-instructions.cc

@@ -2741,7 +2741,7 @@ HConstant::HConstant(double double_value,
 
 
 HConstant::HConstant(ExternalReference reference)
-  : HTemplateInstruction(HType::None()),
+  : HTemplateInstruction<0>(HType::None()),
     has_smi_value_(false),
     has_int32_value_(false),
     has_double_value_(false),