Add decode() functionality to image elements.

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

Index: third_party/WebKit/Source/core/html/HTMLImageElement.cpp
diff --git a/third_party/WebKit/Source/core/html/HTMLImageElement.cpp b/third_party/WebKit/Source/core/html/HTMLImageElement.cpp
index 54cb6398f39bbe0b44d7e9ec637f1c15d4378e72..12ab4a212a276b764febd69289ef401c8a9ff701 100644
--- a/third_party/WebKit/Source/core/html/HTMLImageElement.cpp
+++ b/third_party/WebKit/Source/core/html/HTMLImageElement.cpp
@@ -31,6 +31,7 @@
 #include "core/css/MediaValuesDynamic.h"
 #include "core/css/parser/SizesAttributeParser.h"
 #include "core/dom/Attribute.h"
+#include "core/dom/DOMException.h"
 #include "core/dom/NodeTraversal.h"
 #include "core/dom/shadow/ShadowRoot.h"
 #include "core/frame/Deprecation.h"
@@ -51,6 +52,7 @@
 #include "core/layout/LayoutImage.h"
 #include "core/layout/api/LayoutImageItem.h"
 #include "core/loader/resource/ImageResourceContent.h"
+#include "core/page/ChromeClient.h"
 #include "core/page/Page.h"
 #include "core/style/ContentData.h"
 #include "core/svg/graphics/SVGImageForContainer.h"
@@ -92,6 +94,7 @@ HTMLImageElement::HTMLImageElement(Document& document, bool created_by_parser)
       image_device_pixel_ratio_(1.0f),
       source_(nullptr),
       layout_disposition_(LayoutDisposition::kPrimaryContent),
+      decode_sequence_id_(0),
       form_was_set_by_parser_(false),
       element_created_by_parser_(created_by_parser),
       is_fallback_image_(false),
@@ -115,6 +118,7 @@ DEFINE_TRACE(HTMLImageElement) {
   visitor->Trace(listener_);
   visitor->Trace(form_);
   visitor->Trace(source_);
+  visitor->Trace(decode_promise_resolvers_);
   HTMLElement::Trace(visitor);
 }
 
@@ -125,6 +129,42 @@ void HTMLImageElement::NotifyViewportChanged() {
   SelectSourceURL(ImageLoader::kUpdateSizeChanged);
 }
 
+void HTMLImageElement::RequestDecode() {
+  DCHECK(!decode_promise_resolvers_.IsEmpty());
+  if (!GetImageLoader().GetImage() ||
+      !GetImageLoader().GetImage()->GetImage()) {
+    DidDecode(decode_sequence_id_, false);
+    return;
+  }
+  Image* image = GetImageLoader().GetImage()->GetImage();
+  LocalFrame* frame = GetDocument().GetFrame();

[dcheng, 2017/04/17 18:48:02]

Hmm. I think we might need to null check here.

I think JS could remove the iframe it's running in, and then request decode. In
that case, I think |frame| will be null here.

[vmpstr, 2017/04/17 20:51:25]

Done.

+  frame->GetChromeClient().RequestDecode(
+      frame, image->ImageForCurrentFrame(),
+      WTF::Bind(&HTMLImageElement::DidDecode, WrapWeakPersistent(this),
+                decode_sequence_id_));
+}
+
+void HTMLImageElement::DidDecode(uint32_t sequence_id, bool success) {
+  // If the sequence id attached with this callback doesn't match our current
+  // sequence id, then the source of the image has changed. In other words, the
+  // decode resolved/rejected by this callback was already rejected. Since we
+  // could have had a new decode request, we have to make sure not to
+  // resolve/reject those using the stale callback.
+  if (sequence_id != decode_sequence_id_)
+    return;
+
+  if (success) {
+    for (auto& resolver : decode_promise_resolvers_)
+      resolver->Resolve();
+  } else {
+    for (auto& resolver : decode_promise_resolvers_) {
+      resolver->Reject(DOMException::Create(
+          kEncodingError, "The source image cannot be decoded"));
+    }
+  }
+  decode_promise_resolvers_.Clear();
+}
+
 HTMLImageElement* HTMLImageElement::CreateForJSConstructor(Document& document) {
   HTMLImageElement* image = new HTMLImageElement(document);
   image->element_created_by_parser_ = false;
@@ -260,6 +300,14 @@ void HTMLImageElement::ParseAttribute(
     }
   } else if (name == srcAttr || name == srcsetAttr || name == sizesAttr) {
     SelectSourceURL(ImageLoader::kUpdateIgnorePreviousError);
+    // Ensure to fail any pending decodes on possible source changes.
+    if (!decode_promise_resolvers_.IsEmpty() &&
+        params.old_value != params.new_value) {
+      DidDecode(decode_sequence_id_, false);
+      // Increment the sequence id so that any in flight decode completion tasks
+      // will not trigger promise resolution for new decode requests.
+      ++decode_sequence_id_;
+    }
   } else if (name == usemapAttr) {
     SetIsLink(!params.new_value.IsNull());
   } else if (name == referrerpolicyAttr) {
@@ -596,6 +644,17 @@ int HTMLImageElement::y() const {
   return abs_pos.Y();
 }
 
+ScriptPromise HTMLImageElement::decode(ScriptState* scriptState,
+                                       ExceptionState& exceptionState) {
+  exceptionState.ClearException();
+  decode_promise_resolvers_.push_back(
+      ScriptPromiseResolver::Create(scriptState));
+  ScriptPromise promise = decode_promise_resolvers_.back()->Promise();
+  if (complete())
+    RequestDecode();
+  return promise;
+}
+
 bool HTMLImageElement::complete() const {
   return GetImageLoader().ImageComplete();
 }
@@ -612,8 +671,8 @@ bool HTMLImageElement::IsServerMap() const {
 
   const AtomicString& usemap = FastGetAttribute(usemapAttr);
 
-  // If the usemap attribute starts with '#', it refers to a map element in the
-  // document.
+  // If the usemap attribute starts with '#', it refers to a map element in
+  // the document.
   if (usemap[0] == '#')
     return false;
 
@@ -833,6 +892,15 @@ PassRefPtr<ComputedStyle> HTMLImageElement::CustomStyleForLayoutObject() {
   }
 }
 
+void HTMLImageElement::ImageNotifyFinished(bool success) {
+  if (decode_promise_resolvers_.IsEmpty())
+    return;
+  if (success)
+    RequestDecode();
+  else
+    DidDecode(decode_sequence_id_, false);
+}
+
 IntSize HTMLImageElement::BitmapSourceSize() const {
   ImageResourceContent* image = CachedImage();
   if (!image)