[stubs] Cleanup FixedArray copying builtin

src/code-stub-assembler.h

Index: src/code-stub-assembler.h
diff --git a/src/code-stub-assembler.h b/src/code-stub-assembler.h
index a51827b28f51cf6817fcce4ba8cf0da9a7bee472..a11f4a79d9dd1c3044441683315871ee4f00d765 100644
--- a/src/code-stub-assembler.h
+++ b/src/code-stub-assembler.h
@@ -287,7 +287,8 @@ class CodeStubAssembler : public compiler::CodeAssembler {
 
   compiler::Node* AllocateFixedArray(ElementsKind kind,
                                      compiler::Node* capacity,
-                                     ParameterMode mode = INTEGER_PARAMETERS);
+                                     ParameterMode mode = INTEGER_PARAMETERS,
+                                     AllocationFlags flags = kNone);
 
   void FillFixedArrayWithHole(ElementsKind kind, compiler::Node* array,
                               compiler::Node* from_index,
@@ -548,6 +549,13 @@ class CodeStubAssembler : public compiler::CodeAssembler {
       compiler::Node* feedback_vector, compiler::Node* slot,
       compiler::Node* value);
 
+  compiler::Node* GetFixedAarrayAllocationSize(compiler::Node* element_count,
+                                               ElementsKind kind,
+                                               ParameterMode mode) {
+    return ElementOffsetFromIndex(element_count, kind, mode,
+                                  FixedArray::kHeaderSize);
+  }
+
  private:
   enum ElementSupport { kOnlyProperties, kSupportElements };