[objects] Declaring SFI::get_api_func_data as const

The method has been non-const since initially introduced in de070ccf.
Here's a minor change to make it const, for it may/shall be, for other
similar methods are, and for making it easier for future changes
(accessing this method in another const method, etc.).

Change-Id: I3449214fc086403fc9b24b6f502ca20ac0b1426a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2055123Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66270}

src/objects/shared-function-info-inl.h

@@ -432,7 +432,7 @@ bool SharedFunctionInfo::IsApiFunction() const {
   return function_data().IsFunctionTemplateInfo();
 }
 
-FunctionTemplateInfo SharedFunctionInfo::get_api_func_data() {
+FunctionTemplateInfo SharedFunctionInfo::get_api_func_data() const {
   DCHECK(IsApiFunction());
   return FunctionTemplateInfo::cast(function_data());
 }

src/objects/shared-function-info.h

@@ -309,7 +309,7 @@ class SharedFunctionInfo : public HeapObject {
 
   inline bool IsApiFunction() const;
   inline bool is_class_constructor() const;
-  inline FunctionTemplateInfo get_api_func_data();
+  inline FunctionTemplateInfo get_api_func_data() const;
   inline void set_api_func_data(FunctionTemplateInfo data);
   inline bool HasBytecodeArray() const;
   inline BytecodeArray GetBytecodeArray() const;