Merge r5471 into 2.3 branch....

src/x64/ic-x64.cc

Index: src/x64/ic-x64.cc
===================================================================
--- src/x64/ic-x64.cc	(revision 5471)
+++ src/x64/ic-x64.cc	(working copy)
@@ -755,7 +755,6 @@
   //  -- rsp[0] : return address
   // -----------------------------------
   Label miss;
-  Label index_out_of_range;
 
   Register receiver = rdx;
   Register index = rax;
@@ -770,7 +769,7 @@
                                           result,
                                           &miss,  // When not a string.
                                           &miss,  // When not a number.
-                                          &index_out_of_range,
+                                          &miss,  // When index out of range.
                                           STRING_INDEX_IS_ARRAY_INDEX);
   char_at_generator.GenerateFast(masm);
   __ ret(0);
@@ -778,10 +777,6 @@
   ICRuntimeCallHelper call_helper;
   char_at_generator.GenerateSlow(masm, call_helper);
 
-  __ bind(&index_out_of_range);
-  __ LoadRoot(rax, Heap::kUndefinedValueRootIndex);
-  __ ret(0);
-
   __ bind(&miss);
   GenerateMiss(masm);
 }