Revert "[arraybuffer] Organize views in a hash_set"

This reverts commit f366e7dd.

Reason for revert: Performance regression, see https://crbug.com/1026763.
The original implementation optimized better for the case where there exists
exactly one view.

Original change's description:
> [arraybuffer] Organize views in a hash_set
>
> This is a first step of getting rid of blink::ArrayBuffer.
>
> blink::ArrayBuffer serves two purposes by now:
> 1) Managing a list of ArrayBufferViews;
> 2) Managing the detached flag;
>
> With this CL I encapsulate the list of ArrayBufferViews. In follow-up
> CLs I then want to pass the list and an ArrayBufferContents object
> to the ArrayBufferView instead of the ArrayBuffer object. This will
> bring us one step closer to removing blink::ArrayBuffer.
>
> Update: ArrayBuffer seems to be very involved. It is the connecting
> data structure between DOMArrayBuffer, ArrayBufferContents, and
> ArrayBufferView. Even though it is not used anymore outside these
> classes, it is not obvious if we can replace it within these classes.
> I still think that refactoring the organization of views here is
> good.
>
> R=​haraken@chromium.org
>
> Bug: chromium:1008840
> Change-Id: I533f5496b7c51312e77a0138ac8249f9f0e55ffd
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1911207
> Reviewed-by: Kentaro Hara <haraken@chromium.org>
> Commit-Queue: Andreas Haas <ahaas@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#714880}

TBR=haraken@chromium.org,ahaas@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: chromium:1008840, chromium:1026763
Change-Id: Ifad3b3b8cf46290b9bf0f2d4ef958fdd7c414ed4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1930817Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718117}

third_party/blink/renderer/core/typed_arrays/array_buffer/array_buffer.cc

@@ -30,13 +30,6 @@
 
 namespace blink {
 
-ArrayBuffer::ArrayBuffer(ArrayBufferContents& contents) : is_detached_(false) {
-  if (contents.IsShared())
-    contents.ShareWith(contents_);
-  else
-    contents.Transfer(contents_);
-}
-
 bool ArrayBuffer::Transfer(ArrayBufferContents& result) {
   DCHECK(!IsShared());
   scoped_refptr<ArrayBuffer> keep_alive(this);
@@ -47,19 +40,19 @@ bool ArrayBuffer::Transfer(ArrayBufferContents& result) {
   }
 
   bool all_views_are_detachable = true;
-  for (auto* view : views_) {
-    if (!view->IsDetachable()) {
+  for (ArrayBufferView* i = first_view_; i; i = i->next_view_) {
+    if (!i->IsDetachable())
       all_views_are_detachable = false;
-    }
   }
 
   if (all_views_are_detachable) {
     contents_.Transfer(result);
 
-    for (auto* view : views_) {
-      view->Detach();
+    while (first_view_) {
+      ArrayBufferView* current = first_view_;
+      RemoveView(current);
+      current->Detach();
     }
-    views_.clear();
 
     is_detached_ = true;
   } else {
@@ -103,12 +96,23 @@ bool ArrayBuffer::ShareNonSharedForInternalUse(ArrayBufferContents& result) {
 }
 
 void ArrayBuffer::AddView(ArrayBufferView* view) {
-  views_.insert(view);
+  view->buffer_ = this;
+  view->prev_view_ = nullptr;
+  view->next_view_ = first_view_;
+  if (first_view_)
+    first_view_->prev_view_ = view;
+  first_view_ = view;
 }
 
 void ArrayBuffer::RemoveView(ArrayBufferView* view) {
-  DCHECK(views_.Contains(view));
-  views_.erase(view);
+  DCHECK_EQ(this, view->buffer_.get());
+  if (view->next_view_)
+    view->next_view_->prev_view_ = view->prev_view_;
+  if (view->prev_view_)
+    view->prev_view_->next_view_ = view->next_view_;
+  if (first_view_ == view)
+    first_view_ = view->next_view_;
+  view->prev_view_ = view->next_view_ = nullptr;
 }
 
 }  // namespace blink

third_party/blink/renderer/core/typed_arrays/array_buffer/array_buffer.h

@@ -94,7 +94,7 @@ class CORE_EXPORT ArrayBuffer : public RefCounted<ArrayBuffer> {
   ~ArrayBuffer() = default;
 
  protected:
-  explicit ArrayBuffer(ArrayBufferContents&);
+  inline explicit ArrayBuffer(ArrayBufferContents&);
 
  private:
   static inline scoped_refptr<ArrayBuffer> Create(
@@ -113,7 +113,7 @@ class CORE_EXPORT ArrayBuffer : public RefCounted<ArrayBuffer> {
   inline unsigned ClampIndex(unsigned index) const;
 
   ArrayBufferContents contents_;
-  HashSet<ArrayBufferView*> views_;
+  ArrayBufferView* first_view_;
   bool is_detached_;
 };
 
@@ -207,6 +207,14 @@ scoped_refptr<ArrayBuffer> ArrayBuffer::CreateShared(
   return base::AdoptRef(new ArrayBuffer(contents));
 }
 
+ArrayBuffer::ArrayBuffer(ArrayBufferContents& contents)
+    : first_view_(nullptr), is_detached_(false) {
+  if (contents.IsShared())
+    contents.ShareWith(contents_);
+  else
+    contents.Transfer(contents_);
+}
+
 void* ArrayBuffer::Data() {
   return contents_.Data();
 }

third_party/blink/renderer/core/typed_arrays/array_buffer/array_buffer_view.cc

@@ -33,7 +33,9 @@ ArrayBufferView::ArrayBufferView(scoped_refptr<ArrayBuffer> buffer,
                                  size_t byte_offset)
     : byte_offset_(byte_offset),
       is_detachable_(true),
-      buffer_(std::move(buffer)) {
+      buffer_(std::move(buffer)),
+      prev_view_(nullptr),
+      next_view_(nullptr) {
   base_address_ =
       buffer_ ? (static_cast<char*>(buffer_->DataMaybeShared()) + byte_offset_)
               : nullptr;

third_party/blink/renderer/core/typed_arrays/array_buffer/array_buffer_view.h

@@ -89,6 +89,8 @@ class CORE_EXPORT ArrayBufferView : public RefCounted<ArrayBufferView> {
  private:
   friend class ArrayBuffer;
   scoped_refptr<ArrayBuffer> buffer_;
+  ArrayBufferView* prev_view_;
+  ArrayBufferView* next_view_;
 };
 
 }  // namespace blink