Revert "Revert "Upgrade to 5.0.71.48"" DO NOT MERGE

This reverts commit f2e3994fa5148cc3d9946666f0b0596290192b0e,
and updates the x64 makefile properly so it doesn't break that
build.

FPIIM-449

Change-Id: Ib83e35bfbae6af627451c926a9650ec57c045605
(cherry picked from commit 109988c7ccb6f3fd1a58574fa3dfb88beaef6632)
diff --git a/src/compiler/js-native-context-specialization.h b/src/compiler/js-native-context-specialization.h
index 45ff87f..4251d72 100644
--- a/src/compiler/js-native-context-specialization.h
+++ b/src/compiler/js-native-context-specialization.h
@@ -38,7 +38,8 @@
   // Flags that control the mode of operation.
   enum Flag {
     kNoFlags = 0u,
-    kDeoptimizationEnabled = 1u << 0,
+    kBailoutOnUninitialized = 1u << 0,
+    kDeoptimizationEnabled = 1u << 1,
   };
   typedef base::Flags<Flag> Flags;
 
@@ -50,6 +51,7 @@
   Reduction Reduce(Node* node) final;
 
  private:
+  Reduction ReduceJSLoadContext(Node* node);
   Reduction ReduceJSLoadNamed(Node* node);
   Reduction ReduceJSStoreNamed(Node* node);
   Reduction ReduceJSLoadProperty(Node* node);
@@ -66,11 +68,17 @@
                               LanguageMode language_mode,
                               KeyedAccessStoreMode store_mode);
   Reduction ReduceNamedAccess(Node* node, Node* value,
+                              FeedbackNexus const& nexus, Handle<Name> name,
+                              AccessMode access_mode,
+                              LanguageMode language_mode);
+  Reduction ReduceNamedAccess(Node* node, Node* value,
                               MapHandleList const& receiver_maps,
                               Handle<Name> name, AccessMode access_mode,
                               LanguageMode language_mode,
                               Node* index = nullptr);
 
+  Reduction ReduceSoftDeoptimize(Node* node);
+
   // Adds stability dependencies on all prototypes of every class in
   // {receiver_type} up to (and including) the {holder}.
   void AssumePrototypesStable(Type* receiver_type,