Use Shadow DOM to display fallback content for images

Source/core/paint/ImagePainter.cpp

Index: Source/core/paint/ImagePainter.cpp
diff --git a/Source/core/paint/ImagePainter.cpp b/Source/core/paint/ImagePainter.cpp
index 04ebee1f5e6d0eee700066c2648c8239f05b760e..57ea9efe38bb0f180cd21072e9ab8500c99a2a1a 100644
--- a/Source/core/paint/ImagePainter.cpp
+++ b/Source/core/paint/ImagePainter.cpp
@@ -78,82 +78,20 @@ void ImagePainter::paintReplaced(PaintInfo& paintInfo, const LayoutPoint& paintO
 
     GraphicsContext* context = paintInfo.context;
 
-    if (!m_renderImage.imageResource()->hasImage() || m_renderImage.imageResource()->errorOccurred()) {
+    if (!m_renderImage.imageResource()->hasImage()) {
         if (paintInfo.phase == PaintPhaseSelection)
             return;
 
         if (cWidth > 2 && cHeight > 2) {
-            const int borderWidth = 1;
-
-            LayoutUnit leftBorder = m_renderImage.borderLeft();
-            LayoutUnit topBorder = m_renderImage.borderTop();
-            LayoutUnit leftPad = m_renderImage.paddingLeft();
-            LayoutUnit topPad = m_renderImage.paddingTop();
-
             // Draw an outline rect where the image should be.
-            IntRect paintRect = pixelSnappedIntRect(LayoutRect(paintOffset.x() + leftBorder + leftPad, paintOffset.y() + topBorder + topPad, cWidth, cHeight));
+            IntRect paintRect = pixelSnappedIntRect(LayoutRect(paintOffset.x() + m_renderImage.borderLeft() + m_renderImage.paddingLeft(), paintOffset.y() + m_renderImage.borderTop() + m_renderImage.paddingTop(), cWidth, cHeight));
             DrawingRecorder recorder(context, &m_renderImage, paintInfo.phase, paintRect);
             context->setStrokeStyle(SolidStroke);
             context->setStrokeColor(Color::lightGray);
             context->setFillColor(Color::transparent);
             context->drawRect(paintRect);
-
-            bool errorPictureDrawn = false;
-            LayoutSize imageOffset;
-            // When calculating the usable dimensions, exclude the pixels of
-            // the ouline rect so the error image/alt text doesn't draw on it.
-            LayoutUnit usableWidth = cWidth - 2 * borderWidth;
-            LayoutUnit usableHeight = cHeight - 2 * borderWidth;
-
-            RefPtr<Image> image = m_renderImage.imageResource()->image();
-
-            if (m_renderImage.imageResource()->errorOccurred() && !image->isNull() && usableWidth >= image->width() && usableHeight >= image->height()) {
-                float deviceScaleFactor = blink::deviceScaleFactor(m_renderImage.frame());
-                // Call brokenImage() explicitly to ensure we get the broken image icon at the appropriate resolution.
-                pair<Image*, float> brokenImageAndImageScaleFactor = ImageResource::brokenImage(deviceScaleFactor);
-                image = brokenImageAndImageScaleFactor.first;
-                IntSize imageSize = image->size();
-                imageSize.scale(1 / brokenImageAndImageScaleFactor.second);
-                // Center the error image, accounting for border and padding.
-                LayoutUnit centerX = (usableWidth - imageSize.width()) / 2;
-                if (centerX < 0)
-                    centerX = 0;
-                LayoutUnit centerY = (usableHeight - imageSize.height()) / 2;
-                if (centerY < 0)
-                    centerY = 0;
-                imageOffset = LayoutSize(leftBorder + leftPad + centerX + borderWidth, topBorder + topPad + centerY + borderWidth);
-                context->drawImage(image.get(), pixelSnappedIntRect(LayoutRect(paintOffset + imageOffset, imageSize)), CompositeSourceOver, m_renderImage.shouldRespectImageOrientation());
-                errorPictureDrawn = true;
-            }
-
-            if (!m_renderImage.altText().isEmpty()) {
-                const Font& font = m_renderImage.style()->font();
-                const FontMetrics& fontMetrics = font.fontMetrics();
-                LayoutUnit ascent = fontMetrics.ascent();
-                LayoutPoint textRectOrigin = paintOffset;
-                textRectOrigin.move(leftBorder + leftPad + (RenderImage::paddingWidth / 2) - borderWidth, topBorder + topPad + (RenderImage::paddingHeight / 2) - borderWidth);
-                LayoutPoint textOrigin(textRectOrigin.x(), textRectOrigin.y() + ascent);
-
-                // Only draw the alt text if it'll fit within the content box,
-                // and only if it fits above the error image.
-                TextRun textRun = constructTextRun(&m_renderImage, font, m_renderImage.altText(), m_renderImage.style(), TextRun::AllowTrailingExpansion | TextRun::ForbidLeadingExpansion, DefaultTextRunFlags | RespectDirection);
-                float textWidth = font.width(textRun);
-                TextRunPaintInfo textRunPaintInfo(textRun);
-                textRunPaintInfo.bounds = FloatRect(textRectOrigin, FloatSize(textWidth, fontMetrics.height()));
-                context->setFillColor(m_renderImage.resolveColor(CSSPropertyColor));
-                if (textRun.direction() == RTL) {
-                    int availableWidth = cWidth - static_cast<int>(RenderImage::paddingWidth);
-                    textOrigin.move(availableWidth - ceilf(textWidth), 0);
-                }
-                if (errorPictureDrawn) {
-                    if (usableWidth >= textWidth && fontMetrics.height() <= imageOffset.height())
-                        context->drawBidiText(font, textRunPaintInfo, textOrigin);
-                } else if (usableWidth >= textWidth && usableHeight >= fontMetrics.height()) {
-                    context->drawBidiText(font, textRunPaintInfo, textOrigin);
-                }
-            }
         }
-    } else if (m_renderImage.imageResource()->hasImage() && cWidth > 0 && cHeight > 0) {
+    } else if (cWidth > 0 && cHeight > 0) {
         LayoutRect contentRect = m_renderImage.contentBoxRect();
         contentRect.moveBy(paintOffset);
         LayoutRect paintRect = m_renderImage.replacedContentRect();