Refactor platform-specific code for determining shared stub for keyed load/stores.

src/stub-cache.h

Index: src/stub-cache.h
diff --git a/src/stub-cache.h b/src/stub-cache.h
index 8ecf8bbcf58b2570063960fcd4e879f7de3637bf..825529fbee844739d60d68cadb7547a0bc4fcd1d 100644
--- a/src/stub-cache.h
+++ b/src/stub-cache.h
@@ -661,6 +661,8 @@ class KeyedLoadStubCompiler: public StubCompiler {
   MaybeObject* GetCode(PropertyType type,
                        String* name,
                        InlineCacheState state = MONOMORPHIC);
+
+  MaybeObject* ComputeSharedKeyedLoadElementStub(Map* receiver_map);
 };
 
 
@@ -718,6 +720,8 @@ class KeyedStoreStubCompiler: public StubCompiler {
                        String* name,
                        InlineCacheState state = MONOMORPHIC);
 
+  MaybeObject* ComputeSharedKeyedStoreElementStub(Map* receiver_map);
+
   StrictModeFlag strict_mode_;
 };