[explicit isolates] Remove GetHeap/GetIsolate from FixedArray

Change GetHeap() in set methods to Heap::FromWritableHeapObject() since
the object can't be read-only if set is being called on it. Also use the
non-isolate form of set_the_hole to remove one GetIsolate().

Bug: v8:7786
Change-Id: I85cb95c8c7eb3baa9316b4a39eecf21bb13e5958
Reviewed-on: https://chromium-review.googlesource.com/1128081
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Leszek Swirski <leszeks@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54301}

src/objects/fixed-array-inl.h

@@ -97,7 +97,7 @@ void FixedArray::set(int index, Object* value) {
   DCHECK_LT(index, this->length());
   int offset = kHeaderSize + index * kPointerSize;
   RELAXED_WRITE_FIELD(this, offset, value);
-  WRITE_BARRIER(GetHeap(), this, offset, value);
+  WRITE_BARRIER(Heap::FromWritableHeapObject(this), this, offset, value);
 }
 
 void FixedArray::set(int index, Object* value, WriteBarrierMode mode) {
@@ -106,7 +106,8 @@ void FixedArray::set(int index, Object* value, WriteBarrierMode mode) {
   DCHECK_LT(index, this->length());
   int offset = kHeaderSize + index * kPointerSize;
   RELAXED_WRITE_FIELD(this, offset, value);
-  CONDITIONAL_WRITE_BARRIER(GetHeap(), this, offset, value, mode);
+  CONDITIONAL_WRITE_BARRIER(Heap::FromWritableHeapObject(this), this, offset,
+                            value, mode);
 }
 
 void FixedArray::NoWriteBarrierSet(FixedArray* array, int index,
@@ -153,9 +154,8 @@ void FixedArray::set_the_hole(ReadOnlyRoots ro_roots, int index) {
 }
 
 void FixedArray::FillWithHoles(int from, int to) {
-  Isolate* isolate = GetIsolate();
   for (int i = from; i < to; i++) {
-    set_the_hole(isolate, i);
+    set_the_hole(i);
   }
 }
 
@@ -243,7 +243,7 @@ void WeakFixedArray::Set(int index, MaybeObject* value) {
   DCHECK_LT(index, length());
   int offset = OffsetOfElementAt(index);
   RELAXED_WRITE_FIELD(this, offset, value);
-  WEAK_WRITE_BARRIER(GetHeap(), this, offset, value);
+  WEAK_WRITE_BARRIER(Heap::FromWritableHeapObject(this), this, offset, value);
 }
 
 void WeakFixedArray::Set(int index, MaybeObject* value, WriteBarrierMode mode) {
@@ -251,7 +251,8 @@ void WeakFixedArray::Set(int index, MaybeObject* value, WriteBarrierMode mode) {
   DCHECK_LT(index, length());
   int offset = OffsetOfElementAt(index);
   RELAXED_WRITE_FIELD(this, offset, value);
-  CONDITIONAL_WEAK_WRITE_BARRIER(GetHeap(), this, offset, value, mode);
+  CONDITIONAL_WEAK_WRITE_BARRIER(Heap::FromWritableHeapObject(this), this,
+                                 offset, value, mode);
 }
 
 MaybeObject** WeakFixedArray::data_start() {
@@ -277,7 +278,8 @@ void WeakArrayList::Set(int index, MaybeObject* value, WriteBarrierMode mode) {
   DCHECK_LT(index, this->capacity());
   int offset = OffsetOfElementAt(index);
   RELAXED_WRITE_FIELD(this, offset, value);
-  CONDITIONAL_WEAK_WRITE_BARRIER(GetHeap(), this, offset, value, mode);
+  CONDITIONAL_WEAK_WRITE_BARRIER(Heap::FromWritableHeapObject(this), this,
+                                 offset, value, mode);
 }
 
 MaybeObject** WeakArrayList::data_start() {