Add support for IncrementCounter in Hydrogen.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 2cec68b097573eab83f941c03940b01647f2e3e9..19507e0b01f453166c19b09dc6391171658ba661 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -2003,6 +2003,8 @@ LInstruction* LChunkBuilder::DoConstant(HConstant* instr) {
   } else if (r.IsDouble()) {
     LOperand* temp = TempRegister();
     return DefineAsRegister(new(zone()) LConstantD(temp));
+  } else if (r.IsExternal()) {
+    return DefineAsRegister(new(zone()) LConstantE);
   } else if (r.IsTagged()) {
     return DefineAsRegister(new(zone()) LConstantT);
   } else {