Merged: Math.sign fixes (Squashed multiple commits).

src/compiler/simplified-lowering.cc

Index: src/compiler/simplified-lowering.cc
diff --git a/src/compiler/simplified-lowering.cc b/src/compiler/simplified-lowering.cc
index de64de3e1fd7cf0c15b72f21a6fa2a6baad36a27..d698fe926939ed60e11de7cfdc686e9fa3841451 100644
--- a/src/compiler/simplified-lowering.cc
+++ b/src/compiler/simplified-lowering.cc
@@ -2977,7 +2977,7 @@ Node* SimplifiedLowering::Float64Sign(Node* const node) {
       graph()->NewNode(
           common()->Select(MachineRepresentation::kFloat64),
           graph()->NewNode(machine()->Float64LessThan(), zero, input), one,
-          zero));
+          input));
 }
 
 Node* SimplifiedLowering::Int32Abs(Node* const node) {