Use Shadow DOM to display fallback content for images

Source/core/html/HTMLImageLoader.cpp

Index: Source/core/html/HTMLImageLoader.cpp
diff --git a/Source/core/html/HTMLImageLoader.cpp b/Source/core/html/HTMLImageLoader.cpp
index 44fc879fe2f85abc3b3d5fe90ff5fef691766d39..baced28215a3bd5c6556caf011e80b1dcecef008 100644
--- a/Source/core/html/HTMLImageLoader.cpp
+++ b/Source/core/html/HTMLImageLoader.cpp
@@ -27,6 +27,7 @@
 #include "core/events/Event.h"
 #include "core/fetch/ImageResource.h"
 #include "core/html/HTMLImageElement.h"
+#include "core/html/HTMLInputElement.h"
 #include "core/html/HTMLObjectElement.h"
 #include "core/html/parser/HTMLParserIdioms.h"
 #include "platform/Logging.h"
@@ -61,6 +62,16 @@ String HTMLImageLoader::sourceURI(const AtomicString& attr) const
     return stripLeadingAndTrailingHTMLSpaces(attr);
 }
 
+void HTMLImageLoader::noImageResourceToLoad()
+{
+    RefPtrWillBeRawPtr<Element> element = this->element();
+    // FIXME: Use fallback content even when there is no alt-text. The only blocker is the large amount of rebaselining it requires.
+    if (isHTMLImageElement(*element) && !toHTMLImageElement(element)->altText().isEmpty())
+        toHTMLImageElement(element)->ensureFallbackContent();
+    if (isHTMLInputElement(*element) && !toHTMLInputElement(element)->altText().isEmpty())
+        toHTMLInputElement(element)->ensureFallbackContent();

[esprehn, 2014/09/05 00:47:51]

Lets just add a virtual method.

[rhogan, 2014/09/08 19:52:42]

Done.

+}
+
 void HTMLImageLoader::notifyFinished(Resource*)
 {
     ImageResource* cachedImage = image();
@@ -69,6 +80,19 @@ void HTMLImageLoader::notifyFinished(Resource*)
     ImageLoader::notifyFinished(cachedImage);
 
     bool loadError = cachedImage->errorOccurred() || cachedImage->response().httpStatusCode() >= 400;
+    if (isHTMLImageElement(*element)) {
+        if (loadError)
+            toHTMLImageElement(element)->ensureFallbackContent();
+        else
+            toHTMLImageElement(element)->ensurePrimaryContent();
+    }
+
+    if (isHTMLInputElement(*element)) {
+        if (loadError)
+            toHTMLInputElement(element)->ensureFallbackContent();

[esprehn, 2014/09/05 00:47:51]

virtual.

[rhogan, 2014/09/08 19:52:42]

Done.

+        else
+            toHTMLInputElement(element)->ensurePrimaryContent();
+    }
 
     if (loadError && isHTMLObjectElement(*element))
         toHTMLObjectElement(element)->renderFallbackContent();