Add faster, but unsafe version of LoadInternalField.

src/fast-accessor-assembler.h

Index: src/fast-accessor-assembler.h
diff --git a/src/fast-accessor-assembler.h b/src/fast-accessor-assembler.h
index 41337a2b09d8883efd2243e785040da4db4bfde3..b9bfdc5aaef824869988de8da4f012c1ee5ceefc 100644
--- a/src/fast-accessor-assembler.h
+++ b/src/fast-accessor-assembler.h
@@ -54,6 +54,15 @@ class FastAccessorAssembler {
   ValueId IntegerConstant(int int_constant);
   ValueId GetReceiver();
   ValueId LoadInternalField(ValueId value_id, int field_no);
+
+  // Loads internal field and assumes the object is indeed a valid API object
+  // with the proper internal fields present.
+  // The intended use is to call this on an object whose structure has already
+  // been checked previously, e.g. the accessor's receiver, which is map-checked
+  // before the fast accessor is called on it. Using this on an arbitrary object
+  // will result in unsafe memory accesses.
+  ValueId LoadInternalFieldUnchecked(ValueId value_id, int field_no);
+
   ValueId LoadValue(ValueId value_id, int offset);
   ValueId LoadObject(ValueId value_id, int offset);
 
@@ -77,6 +86,8 @@ class FastAccessorAssembler {
   compiler::Node* FromId(ValueId value) const;
   CodeStubAssembler::Label* FromId(LabelId value) const;
 
+  void CheckIsJSObjectOrJump(ValueId value, LabelId label_id);
+
   void Clear();
   Zone* zone() { return &zone_; }
   Isolate* isolate() const { return isolate_; }