Use Shadow DOM to display fallback content for images

Source/core/editing/TextIterator.cpp

Index: Source/core/editing/TextIterator.cpp
diff --git a/Source/core/editing/TextIterator.cpp b/Source/core/editing/TextIterator.cpp
index 2fad13588cfa45747555c261c1aacff8826cf7e9..55c41c7a5ed754762f4625c85582ca58647d76b8 100644
--- a/Source/core/editing/TextIterator.cpp
+++ b/Source/core/editing/TextIterator.cpp
@@ -37,6 +37,7 @@
 #include "core/editing/htmlediting.h"
 #include "core/frame/FrameView.h"
 #include "core/html/HTMLElement.h"
+#include "core/html/HTMLImageElement.h"
 #include "core/html/HTMLTextFormControlElement.h"
 #include "core/rendering/InlineTextBox.h"
 #include "core/rendering/RenderImage.h"
@@ -467,6 +468,7 @@ void TextIterator::advance()
                     || (m_node && m_node->isHTMLElement()
                     && (isHTMLFormControlElement(toHTMLElement(*m_node))
                     || isHTMLLegendElement(toHTMLElement(*m_node))
+                    || isHTMLImageElement(toElement(*m_node))
                     || isHTMLMeterElement(toHTMLElement(*m_node))
                     || isHTMLProgressElement(toHTMLElement(*m_node)))))) {
                     handledNode = handleReplacedElement();
@@ -829,9 +831,14 @@ bool TextIterator::handleReplacedElement()
     m_positionEndOffset = 1;
     m_singleCharacterBuffer = 0;
 
-    if (m_emitsImageAltText && renderer->isImage() && renderer->isRenderImage()) {
-        m_text = toRenderImage(renderer)->altText();
-        if (!m_text.isEmpty()) {
+    if (m_emitsImageAltText) {
+        bool isTextModified = false;
+        if (isHTMLImageElement(toElement(*m_node))) {
+            m_text = toHTMLImageElement(m_node)->altText();
+            isTextModified = true;
+        }
+
+        if (!m_text.isEmpty() && isTextModified) {
             m_textLength = m_text.length();
             m_lastCharacter = m_text[m_textLength - 1];
             return true;
@@ -1313,7 +1320,7 @@ void SimplifiedBackwardsTextIterator::advance()
                 // FIXME: What about CDATA_SECTION_NODE?
                 if (renderer->style()->visibility() == VISIBLE && m_offset > 0)
                     m_handledNode = handleTextNode();
-            } else if (renderer && (renderer->isImage() || renderer->isWidget())) {
+            } else if (renderer && (isHTMLImageElement(toElement(*m_node)) || renderer->isWidget())) {

[esprehn, 2014/09/05 00:47:50]

I think this breaks image inputs, they're also RenderImage I think.

[rhogan, 2014/09/08 19:52:41]

Done

                 if (renderer->style()->visibility() == VISIBLE && m_offset > 0)
                     m_handledNode = handleReplacedElement();
             } else {