Add decode() functionality to image elements.

third_party/WebKit/Source/core/html/HTMLImageElement.h

Index: third_party/WebKit/Source/core/html/HTMLImageElement.h
diff --git a/third_party/WebKit/Source/core/html/HTMLImageElement.h b/third_party/WebKit/Source/core/html/HTMLImageElement.h
index a85704f6f9d78973489f94032d4cdfaf13dd71cf..179ce6b7e4bb15efe41ccabfe6f9164695d4d455 100644
--- a/third_party/WebKit/Source/core/html/HTMLImageElement.h
+++ b/third_party/WebKit/Source/core/html/HTMLImageElement.h
@@ -32,6 +32,7 @@
 #include "core/html/canvas/CanvasImageElementSource.h"
 #include "core/imagebitmap/ImageBitmapSource.h"
 #include "platform/graphics/GraphicsTypes.h"
+#include "platform/heap/HeapAllocator.h"
 #include "platform/loader/fetch/FetchParameters.h"
 #include "platform/loader/fetch/ResourceResponse.h"
 
@@ -102,6 +103,8 @@ class CORE_EXPORT HTMLImageElement final
   int x() const;
   int y() const;
 
+  ScriptPromise decode(ScriptState*, ExceptionState&);
+
   bool complete() const;
 
   bool HasPendingActivity() const final {
@@ -144,6 +147,8 @@ class CORE_EXPORT HTMLImageElement final
   FormAssociated* ToFormAssociatedOrNull() override { return this; };
   void AssociateWith(HTMLFormElement*) override;
 
+  void ImageNotifyFinished(bool success);
+
  protected:
   // Controls how an image element appears in the layout. See:
   // https://html.spec.whatwg.org/multipage/embedded-content.html#image-request
@@ -196,6 +201,9 @@ class CORE_EXPORT HTMLImageElement final
   bool IsInteractiveContent() const override;
   Image* ImageContents() override;
 
+  void RequestDecode();
+  void DidDecode(uint32_t sequence_id, bool success);
+
   void ResetFormOwner();
   ImageCandidate FindBestFitImageFromPictureParent();
   void SetBestFitURLAndDPRFromImageCandidate(const ImageCandidate&);
@@ -210,6 +218,8 @@ class CORE_EXPORT HTMLImageElement final
   float image_device_pixel_ratio_;
   Member<HTMLSourceElement> source_;
   LayoutDisposition layout_disposition_;
+  HeapVector<Member<ScriptPromiseResolver>> decode_promise_resolvers_;
+  uint32_t decode_sequence_id_;
   unsigned form_was_set_by_parser_ : 1;
   unsigned element_created_by_parser_ : 1;
   unsigned is_fallback_image_ : 1;