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 65a62298cce0df18ec5385e44e6dabffda759bac..9a283310240d920a3fa06eccad9c7b224430fe81 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"
@@ -95,7 +97,8 @@ HTMLImageElement::HTMLImageElement(Document& document, bool createdByParser)
       m_formWasSetByParser(false),
       m_elementCreatedByParser(createdByParser),
       m_isFallbackImage(false),
-      m_referrerPolicy(ReferrerPolicyDefault) {
+      m_referrerPolicy(ReferrerPolicyDefault),
+      m_weakPtrFactory(this) {
   setHasCustomStyleCallbacks();
 }
 
@@ -108,13 +111,16 @@ HTMLImageElement* HTMLImageElement::create(Document& document,
   return new HTMLImageElement(document, createdByParser);
 }
 
-HTMLImageElement::~HTMLImageElement() {}
+HTMLImageElement::~HTMLImageElement() {
+  m_weakPtrFactory.revokeAll();
+}
 
 DEFINE_TRACE(HTMLImageElement) {
   visitor->trace(m_imageLoader);
   visitor->trace(m_listener);
   visitor->trace(m_form);
   visitor->trace(m_source);
+  visitor->trace(m_decodePromiseResolvers);
   HTMLElement::trace(visitor);
 }
 
@@ -125,6 +131,37 @@ void HTMLImageElement::notifyViewportChanged() {
   selectSourceURL(ImageLoader::UpdateSizeChanged);
 }
 
+void HTMLImageElement::requestDecode() {
+  DCHECK(!m_decodePromiseResolvers.isEmpty());
+  if (!imageLoader().image() || !imageLoader().image()->getImage()) {
+    didDecode(false);
+    return;
+  }
+  Image* image = imageLoader().image()->getImage();
+  auto* page = document().page();
+  if (page) {
+    page->chromeClient().requestDecode(

[dcheng, 2017/04/12 06:53:16]

After reading this through, I think it's fine to just plumb through the
document's frame() here.

Then, as previously mentioned, ChromeClientImpl will use the frame to look up
the LocalRoot(), and then get the WebLocalFrameImpl from that, and then get its
WebFrameWidgetBase from that. From there, we can use the WebLayerTreeView to
enter cc.

[vmpstr, 2017/04/17 18:13:11]

Done. Let me know if this looks better...

+        image->imageForCurrentFrame(),
+        WTF::bind(&HTMLImageElement::didDecode,
+                  m_weakPtrFactory.createWeakPtr()));

[kouhei (in TOK), 2017/04/07 14:26:28]

wrapWeakPersistent(this)?

[vmpstr, 2017/04/07 20:43:43]

Hmm, we have to revoke the weak ptrs if the src of the image changes, since we
might get callbacks for the wrong image. Is that possible with weak persistent?

[dcheng, 2017/04/12 06:53:16]

Other potential options:
- PostCancellableTask, which encapsulates this logic internally:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/platform/WebTa...

- Use a sequence number when the source changes

(I am not sure how common it is to use WeakPtrFactory with Oilpan objects, but
it does seem a bit unusual)

[vmpstr, 2017/04/17 18:13:11]

Done, I used a sequence number here with wrapWeakPersistent.

+  }
+}
+
+void HTMLImageElement::didDecode(bool success) {
+  if (m_decodePromiseResolvers.isEmpty())
+    return;
+  if (success) {
+    for (auto& resolver : m_decodePromiseResolvers)
+      resolver->resolve();
+  } else {
+    for (auto& resolver : m_decodePromiseResolvers) {
+      resolver->reject(DOMException::create(
+          EncodingError, "The source image cannot be decoded"));
+    }
+  }
+  m_decodePromiseResolvers.clear();
+}
+
 HTMLImageElement* HTMLImageElement::createForJSConstructor(Document& document) {
   HTMLImageElement* image = new HTMLImageElement(document);
   image->m_elementCreatedByParser = false;
@@ -260,6 +297,12 @@ void HTMLImageElement::parseAttribute(
     }
   } else if (name == srcAttr || name == srcsetAttr || name == sizesAttr) {
     selectSourceURL(ImageLoader::UpdateIgnorePreviousError);
+    // Ensure to fail any pending decodes on possible source changes.
+    if (!m_decodePromiseResolvers.isEmpty() &&
+        params.oldValue != params.newValue) {
+      didDecode(false);
+      m_weakPtrFactory.revokeAll();
+    }
   } else if (name == usemapAttr) {
     setIsLink(!params.newValue.isNull());
   } else if (name == referrerpolicyAttr) {
@@ -415,9 +458,8 @@ Node::InsertionNotificationRequest HTMLImageElement::insertedInto(
 }
 
 void HTMLImageElement::removedFrom(ContainerNode* insertionPoint) {
-  if (!m_form ||
-      NodeTraversal::highestAncestorOrSelf(*m_form.get()) !=
-          NodeTraversal::highestAncestorOrSelf(*this))
+  if (!m_form || NodeTraversal::highestAncestorOrSelf(*m_form.get()) !=
+                     NodeTraversal::highestAncestorOrSelf(*this))
     resetFormOwner();
   if (m_listener) {
     document().mediaQueryMatcher().removeViewportListener(m_listener);
@@ -524,9 +566,9 @@ const String& HTMLImageElement::currentSrc() const {
   // Return the picked URL string in case of load error.
   if (imageLoader().hadError())
     return m_bestFitImageURL;
-  // Initially, the pending request turns into current request when it is either
-  // available or broken.  We use the image's dimensions as a proxy to it being
-  // in any of these states.
+  // Initially, the pending request turns into current request when it is
+  // either available or broken.  We use the image's dimensions as a proxy to
+  // it being in any of these states.
   if (!imageLoader().image() || !imageLoader().image()->getImage() ||
       !imageLoader().image()->getImage()->width())
     return emptyAtom;
@@ -592,6 +634,17 @@ int HTMLImageElement::y() const {
   return absPos.y();
 }
 
+ScriptPromise HTMLImageElement::decode(ScriptState* scriptState,
+                                       ExceptionState& exceptionState) {
+  exceptionState.clearException();
+  m_decodePromiseResolvers.push_back(
+      ScriptPromiseResolver::create(scriptState));
+  ScriptPromise promise = m_decodePromiseResolvers.back()->promise();
+  if (complete())
+    requestDecode();
+  return promise;
+}
+
 bool HTMLImageElement::complete() const {
   return imageLoader().imageComplete();
 }
@@ -608,8 +661,8 @@ 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;
 
@@ -799,8 +852,8 @@ void HTMLImageElement::setLayoutDisposition(LayoutDisposition layoutDisposition,
 
   m_layoutDisposition = layoutDisposition;
 
-  // This can happen inside of attachLayoutTree() in the middle of a recalcStyle
-  // so we need to reattach synchronously here.
+  // This can happen inside of attachLayoutTree() in the middle of a
+  // recalcStyle so we need to reattach synchronously here.
   if (document().inStyleRecalc()) {
     reattachLayoutTree();
   } else {
@@ -826,6 +879,15 @@ PassRefPtr<ComputedStyle> HTMLImageElement::customStyleForLayoutObject() {
   }
 }
 
+void HTMLImageElement::imageNotifyFinished(bool success) {
+  if (m_decodePromiseResolvers.isEmpty())
+    return;
+  if (success)
+    requestDecode();
+  else
+    didDecode(false);
+}
+
 IntSize HTMLImageElement::bitmapSourceSize() const {
   ImageResourceContent* image = cachedImage();
   if (!image)