Use Shadow DOM to display fallback content for images

Source/core/rendering/RenderImage.cpp

Index: Source/core/rendering/RenderImage.cpp
diff --git a/Source/core/rendering/RenderImage.cpp b/Source/core/rendering/RenderImage.cpp
index d22459a9c54785fc6be3fd635bcf7a07354f191a..24d11ab9aeac21239da827cc896c98a71b13f2b6 100644
--- a/Source/core/rendering/RenderImage.cpp
+++ b/Source/core/rendering/RenderImage.cpp
@@ -60,7 +60,6 @@ RenderImage::RenderImage(Element* element)
     , m_isGeneratedContent(false)
     , m_imageDevicePixelRatio(1.0f)
 {
-    updateAltText();
     ResourceLoadPriorityOptimizer::resourceLoadPriorityOptimizer()->addRenderObject(this);
 }
 
@@ -89,58 +88,6 @@ void RenderImage::setImageResource(PassOwnPtr<RenderImageResource> imageResource
     m_imageResource->initialize(this);
 }
 
-// Alt text is restricted to this maximum size, in pixels.  These are
-// signed integers because they are compared with other signed values.
-static const float maxAltTextWidth = 1024;
-static const int maxAltTextHeight = 256;
-
-IntSize RenderImage::imageSizeForError(ImageResource* newImage) const
-{
-    ASSERT_ARG(newImage, newImage);
-    ASSERT_ARG(newImage, newImage->imageForRenderer(this));
-
-    IntSize imageSize;
-    if (newImage->willPaintBrokenImage()) {
-        float deviceScaleFactor = blink::deviceScaleFactor(frame());
-        pair<Image*, float> brokenImageAndImageScaleFactor = ImageResource::brokenImage(deviceScaleFactor);
-        imageSize = brokenImageAndImageScaleFactor.first->size();
-        imageSize.scale(1 / brokenImageAndImageScaleFactor.second);
-    } else
-        imageSize = newImage->imageForRenderer(this)->size();
-
-    // imageSize() returns 0 for the error image. We need the true size of the
-    // error image, so we have to get it by grabbing image() directly.
-    return IntSize(paddingWidth + imageSize.width() * style()->effectiveZoom(), paddingHeight + imageSize.height() * style()->effectiveZoom());
-}
-
-// Sets the image height and width to fit the alt text.  Returns true if the
-// image size changed.
-bool RenderImage::setImageSizeForAltText(ImageResource* newImage /* = 0 */)
-{
-    IntSize imageSize;
-    if (newImage && newImage->imageForRenderer(this))
-        imageSize = imageSizeForError(newImage);
-    else if (!m_altText.isEmpty() || newImage) {
-        // If we'll be displaying either text or an image, add a little padding.
-        imageSize = IntSize(paddingWidth, paddingHeight);
-    }
-
-    // we have an alt and the user meant it (its not a text we invented)
-    if (!m_altText.isEmpty()) {
-        FontCachePurgePreventer fontCachePurgePreventer;
-
-        const Font& font = style()->font();
-        IntSize paddedTextSize(paddingWidth + std::min(ceilf(font.width(constructTextRun(this, font, m_altText, style()))), maxAltTextWidth), paddingHeight + std::min(font.fontMetrics().height(), maxAltTextHeight));
-        imageSize = imageSize.expandedTo(paddedTextSize);
-    }
-
-    if (imageSize == intrinsicSize())
-        return false;
-
-    setIntrinsicSize(imageSize);
-    return true;
-}
-
 void RenderImage::imageChanged(WrappedImagePtr newImage, const IntRect* rect)
 {
     if (documentBeingDestroyed())
@@ -166,13 +113,7 @@ void RenderImage::imageChanged(WrappedImagePtr newImage, const IntRect* rect)
         m_didIncrementVisuallyNonEmptyPixelCount = true;
     }
 
-    bool imageSizeChanged = false;
-
-    // Set image dimensions, taking into account the size of the alt text.
-    if (m_imageResource->errorOccurred() || !newImage)
-        imageSizeChanged = setImageSizeForAltText(m_imageResource->cachedImage());
-
-    paintInvalidationOrMarkForLayout(imageSizeChanged, rect);
+    repaintOrMarkForLayout(rect);
 }
 
 void RenderImage::updateIntrinsicSizeIfNeeded(const LayoutSize& newSize)
@@ -191,7 +132,7 @@ void RenderImage::updateInnerContentRect()
         m_imageResource->setContainerSizeForRenderer(containerSize);
 }
 
-void RenderImage::paintInvalidationOrMarkForLayout(bool imageSizeChangedToAccomodateAltText, const IntRect* rect)
+void RenderImage::repaintOrMarkForLayout(const IntRect* rect)
 {
     LayoutSize oldIntrinsicSize = intrinsicSize();
     LayoutSize newIntrinsicSize = m_imageResource->intrinsicSize(style()->effectiveZoom());
@@ -204,7 +145,7 @@ void RenderImage::paintInvalidationOrMarkForLayout(bool imageSizeChangedToAccomo
     if (!containingBlock())
         return;
 
-    bool imageSourceHasChangedSize = oldIntrinsicSize != newIntrinsicSize || imageSizeChangedToAccomodateAltText;
+    bool imageSourceHasChangedSize = oldIntrinsicSize != newIntrinsicSize;
     if (imageSourceHasChangedSize)
         setPreferredLogicalWidthsDirty();
 
@@ -300,7 +241,7 @@ void RenderImage::areaElementFocusChanged(HTMLAreaElement* areaElement)
     paintInvalidationRect.moveBy(-absoluteContentBox().location());
     paintInvalidationRect.inflate(outlineWidth);
 
-    paintInvalidationOrMarkForLayout(false, &paintInvalidationRect);
+    repaintOrMarkForLayout(&paintInvalidationRect);
 }
 
 bool RenderImage::boxShadowShouldBeAppliedToBackground(BackgroundBleedAvoidance bleedAvoidance, InlineFlowBox*) const
@@ -383,17 +324,6 @@ bool RenderImage::nodeAtPoint(const HitTestRequest& request, HitTestResult& resu
     return inside;
 }
 
-void RenderImage::updateAltText()
-{
-    if (!node())
-        return;
-
-    if (isHTMLInputElement(*node()))
-        m_altText = toHTMLInputElement(node())->altText();
-    else if (isHTMLImageElement(*node()))
-        m_altText = toHTMLImageElement(node())->altText();
-}
-
 void RenderImage::layout()
 {
     RenderReplaced::layout();