Handlify Object::GetPrototype and (most) callers.

src/ic.h

Index: src/ic.h
diff --git a/src/ic.h b/src/ic.h
index ea074ca3a28053ebfcedeac3539c3e4ce9b220bd..35326c92692e693da00af17c3984d35a6516d132 100644
--- a/src/ic.h
+++ b/src/ic.h
@@ -135,9 +135,10 @@ class IC {
   // TODO(verwaest): This currently returns a HeapObject rather than JSObject*
   // since loading the IC for loading the length from strings are stored on
   // the string map directly, rather than on the JSObject-typed prototype.
-  static inline HeapObject* GetCodeCacheHolder(Isolate* isolate,
-                                               Object* object,
-                                               InlineCacheHolderFlag holder);
+  static inline Handle<HeapObject> GetCodeCacheHolder(
+      Isolate* isolate,
+      Handle<Object> object,
+      InlineCacheHolderFlag holder);
 
   static inline InlineCacheHolderFlag GetCodeCacheFlag(HeapType* type);
   static inline Handle<Map> GetCodeCacheHolder(InlineCacheHolderFlag flag,