[GetIsolate] Allow GetIsolate for Context & JSObjects

Add a separate GetIsolate implementation for Context and JSObjects
so that we can continue using it on these context-specific types,
while eventually removing HeapObject::GetIsolate().

Bug: v8:7786
Change-Id: I86c2e12c6878e060338cbd5c3bbe27dcf978e34b
Reviewed-on: https://chromium-review.googlesource.com/1101320
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53746}

src/contexts-inl.h

@@ -39,13 +39,14 @@ Handle<Context> ScriptContextTable::GetContext(Handle<ScriptContextTable> table,
       FixedArray::get(*table, i + kFirstContextSlotIndex, table->GetIsolate()));
 }
 
-
 // static
 Context* Context::cast(Object* context) {
   DCHECK(context->IsContext());
   return reinterpret_cast<Context*>(context);
 }
 
+Isolate* Context::GetIsolate() const { return GetHeap()->isolate(); }
+
 void Context::set_scope_info(ScopeInfo* scope_info) {
   set(SCOPE_INFO_INDEX, scope_info);
 }

src/contexts.h

@@ -439,6 +439,8 @@ class Context : public FixedArray {
   // Conversions.
   static inline Context* cast(Object* context);
 
+  inline Isolate* GetIsolate() const;
+
   // The default context slot layout; indices are FixedArray slot indices.
   enum Field {
     // These slots are in all contexts.

src/feedback-vector-inl.h

@@ -55,6 +55,8 @@ FeedbackVector* FeedbackVector::cast(Object* obj) {
   return reinterpret_cast<FeedbackVector*>(obj);
 }
 
+Isolate* FeedbackVector::GetIsolate() const { return GetHeap()->isolate(); }
+
 int FeedbackMetadata::GetSlotSize(FeedbackSlotKind kind) {
   switch (kind) {
     case FeedbackSlotKind::kForIn:

src/feedback-vector.h

@@ -145,6 +145,8 @@ class FeedbackVector : public HeapObject {
   // Casting.
   static inline FeedbackVector* cast(Object* obj);
 
+  inline Isolate* GetIsolate() const;
+
   inline void ComputeCounts(int* with_type_info, int* generic,
                             int* vector_ic_count);
 

src/objects-inl.h

@@ -1016,6 +1016,8 @@ Isolate* HeapObject::GetIsolate() const {
   return GetHeap()->isolate();
 }
 
+Isolate* JSReceiver::GetIsolate() const { return GetHeap()->isolate(); }
+
 Map* HeapObject::map() const {
   return map_word().ToMap();
 }

src/objects.h

@@ -2101,6 +2101,8 @@ class JSReceiver: public HeapObject {
   // Returns true if there is no slow (ie, dictionary) backing store.
   inline bool HasFastProperties() const;
 
+  inline Isolate* GetIsolate() const;
+
   // Returns the properties array backing store if it
   // exists. Otherwise, returns an empty_property_array when there's a
   // Smi (hash code) or an empty_fixed_array for a fast properties