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..c198b3d6a20c2c1a8fddd564ba91963eda480194 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 +131,38 @@ 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(
+        image->imageForCurrentFrame(),
+        WTF::bind(&HTMLImageElement::didDecode,
+                  m_weakPtrFactory.createWeakPtr()));
+  }
+}
+
+void HTMLImageElement::didDecode(bool success) {
+  if (m_decodePromiseResolvers.isEmpty())
+    return;
+  static auto resolve = [](ScriptPromiseResolver* resolver) {
+    resolver->resolve();
+  };
+  static auto reject = [](ScriptPromiseResolver* resolver) {
+    resolver->reject(DOMException::create(
+        EncodingError, "The source image cannot be decoded"));
+  };
+  auto process = success ? resolve : reject;
+  for (auto& resolver : m_decodePromiseResolvers)
+    process(resolver);
+  m_decodePromiseResolvers.clear();
+}
+
 HTMLImageElement* HTMLImageElement::createForJSConstructor(Document& document) {
   HTMLImageElement* image = new HTMLImageElement(document);
   image->m_elementCreatedByParser = false;
@@ -260,6 +298,12 @@ 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 +459,8 @@ 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 +567,9 @@ 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 +635,17 @@ 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 +662,8 @@ 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 +853,8 @@ 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 +880,18 @@ PassRefPtr<ComputedStyle> HTMLImageElement::customStyleForLayoutObject() {
   }
 }
 
+void HTMLImageElement::defaultEventHandler(Event* event) {
+  HTMLElement::defaultEventHandler(event);
+  if (m_decodePromiseResolvers.isEmpty())
+    return;
+
+  if (event->type() == EventTypeNames::load) {
+    requestDecode();

[hiroshige, 2017/03/31 08:24:24]

This always causes ChromeClient's requestDecode() even the image's decode() is
not called. Doesn't this degrade the performance?

[vmpstr, 2017/03/31 17:00:16]

This only passes here if line 885 is false, which means we have a decode promise
resolver, which means decode was indeed called. I'll add a comment to make it
more clear

+  } else if (event->type() == EventTypeNames::error) {
+    didDecode(false);
+  }
+}
+
 IntSize HTMLImageElement::bitmapSourceSize() const {
   ImageResourceContent* image = cachedImage();
   if (!image)