Adds WebElement::imageContents()

Source/web/WebNode.cpp

Index: Source/web/WebNode.cpp
diff --git a/Source/web/WebNode.cpp b/Source/web/WebNode.cpp
index 9ce1b976448e9ec9b492f5999dc3ff9971ee2c65..416910254ab9c676ced6965faf987fd99f00664d 100644
--- a/Source/web/WebNode.cpp
+++ b/Source/web/WebNode.cpp
@@ -49,6 +49,7 @@
 #include "core/editing/markup.h"
 #include "core/page/Frame.h"
 #include "core/platform/Widget.h"
+#include "core/rendering/RenderImage.h"
 #include "core/rendering/RenderObject.h"
 #include "core/rendering/RenderWidget.h"
 #include "public/platform/WebString.h"
@@ -251,6 +252,30 @@ WebElement WebNode::shadowHost() const
     return WebElement(coreNode->shadowHost());
 }
 
+WebImage WebNode::imageContents()
+{
+    if (isNull())
+        return WebImage();
+
+    RefPtr<Node> node = unwrap<Node>();
+
+    if (!(node->renderer() && node->renderer()->isImage()))
+        return WebImage();
+
+    WebCore::RenderImage* renderer = toRenderImage(node->renderer());
+    WebCore::CachedImage* cachedImage = renderer->cachedImage();
+    if (!cachedImage || cachedImage->errorOccurred())
+        return WebImage();
+    WebCore::Image* image = cachedImage->imageForRenderer(renderer);

[esprehn, 2013/07/25 22:52:03]

This should be a method on HTMLImageElement and this code should check
isHTMLImageElement(node) and then cast to that and then do image->imageData() or
something like that.

We're trying to get people to stop digging down into the render tree like this.

[jamesr, 2013/07/26 17:54:33]

I don't follow.  This line isn't reaching into the render tree.  We do access
the renderer on line 265, but that's type checked. 
CachedImage::imageForRenderer() is the same as CachedImage::image() except that
it also checks for the image in the SVG image cache (which is keyed by
RenderObject*, for whatever reason) if the image is an SVG image.

If we instead got to the CachedImage by downcasting the Node to HTMLImageElement
this code wouldn't for for elements that generate RenderImages but aren't
HTMLImageElement.  Today, that means HTMLPlugInImageElement and ImageInputType. 
Maybe that'd be OK but it is less general.

+    ASSERT(image);
+
+    RefPtr<NativeImageSkia> bitmap = image->nativeImageForCurrentFrame();
+    if (!bitmap)
+        return WebImage();
+
+    return bitmap->bitmap();
+}
+
 WebNode::WebNode(const PassRefPtr<Node>& node)
     : m_private(node)
 {