[builtins] Introduce proper Float64Tan operator.

src/crankshaft/arm64/lithium-arm64.cc

Index: src/crankshaft/arm64/lithium-arm64.cc
diff --git a/src/crankshaft/arm64/lithium-arm64.cc b/src/crankshaft/arm64/lithium-arm64.cc
index 66eee5caeb2147741beadd3a2603a63a38381e49..32dd971b9bb9f827675a5defe0264a86a3ce1c01 100644
--- a/src/crankshaft/arm64/lithium-arm64.cc
+++ b/src/crankshaft/arm64/lithium-arm64.cc
@@ -1922,13 +1922,6 @@ LInstruction* LChunkBuilder::DoDoubleBits(HDoubleBits* instr) {
 }
 
 
-LInstruction* LChunkBuilder::DoConstructDouble(HConstructDouble* instr) {
-  LOperand* lo = UseRegisterAndClobber(instr->lo());
-  LOperand* hi = UseRegister(instr->hi());
-  return DefineAsRegister(new(zone()) LConstructDouble(hi, lo));
-}
-
-
 LInstruction* LChunkBuilder::DoReturn(HReturn* instr) {
   LOperand* context = info()->IsStub()
       ? UseFixed(instr->context(), cp)