Upgrade V8 to 5.1.281.57  DO NOT MERGE

FPIIM-449

Change-Id: Id981b686b4d587ac31697662eb98bb34be42ad90
(cherry picked from commit 3b9bc31999c9787eb726ecdbfd5796bfdec32a18)
diff --git a/src/compiler/simplified-lowering.h b/src/compiler/simplified-lowering.h
index 358bd97..8b711a9 100644
--- a/src/compiler/simplified-lowering.h
+++ b/src/compiler/simplified-lowering.h
@@ -37,9 +37,6 @@
                     RepresentationChanger* changer);
   void DoStoreBuffer(Node* node);
   void DoShift(Node* node, Operator const* op, Type* rhs_type);
-  void DoStringEqual(Node* node);
-  void DoStringLessThan(Node* node);
-  void DoStringLessThanOrEqual(Node* node);
 
   // TODO(bmeurer): This is a gigantic hack to support the gigantic LoadBuffer
   // typing hack to support the gigantic "asm.js should be fast without proper
@@ -58,7 +55,10 @@
   // position information via the SourcePositionWrapper like all other reducers.
   SourcePositionTable* source_positions_;
 
-  Node* StringComparison(Node* node);
+  Node* Float64Ceil(Node* const node);
+  Node* Float64Floor(Node* const node);
+  Node* Float64Round(Node* const node);
+  Node* Float64Trunc(Node* const node);
   Node* Int32Div(Node* const node);
   Node* Int32Mod(Node* const node);
   Node* Uint32Div(Node* const node);