Reland "Allocation site support for monomorphic StringAdds in BinaryOps".

src/objects.h

Index: src/objects.h
diff --git a/src/objects.h b/src/objects.h
index 17b92d0cc87e5d6258b551fb7bb534f8de76228c..91a2aea2b8868b221bf13dcd31e9953d148f313d 100644
--- a/src/objects.h
+++ b/src/objects.h
@@ -1104,9 +1104,10 @@ class MaybeObject BASE_EMBEDDED {
     "DoPushArgument not implemented for double type")                         \
   V(kEmitLoadRegisterUnsupportedDoubleImmediate,                              \
     "EmitLoadRegister: Unsupported double immediate")                         \
-  V(kEval, "Eval")                                                            \
+  V(kEval, "eval")                                                            \
   V(kExpected0AsASmiSentinel, "Expected 0 as a Smi sentinel")                 \
-  V(kExpectedAlignmentMarker, "Expected alignment marker")                    \
+  V(kExpectedAlignmentMarker, "expected alignment marker")                    \
+  V(kExpectedAllocationSite, "expected allocation site")                      \
   V(kExpectedAllocationSiteInCell,                                            \
     "Expected AllocationSite in property cell")                               \
   V(kExpectedPropertyCellInRegisterA2,                                        \
@@ -5247,6 +5248,9 @@ class Code: public HeapObject {
   Object* FindNthObject(int n, Map* match_map);
   void ReplaceNthObject(int n, Map* match_map, Object* replace_with);
 
+  // Find the first allocation site in an IC stub.
+  AllocationSite* FindFirstAllocationSite();
+
   // Find the first map in an IC stub.
   Map* FindFirstMap();
   void FindAllMaps(MapHandleList* maps);