Enable general CSS filters in the software compositor

cc/output/software_renderer.cc

Index: cc/output/software_renderer.cc
diff --git a/cc/output/software_renderer.cc b/cc/output/software_renderer.cc
index 38d65b75cd00ef32cf4d915f3616a1025480a283..7dc4f798422c1b2579a8a4395d982c4d6a7d071b 100644
--- a/cc/output/software_renderer.cc
+++ b/cc/output/software_renderer.cc
@@ -437,11 +437,10 @@ void SoftwareRenderer::DrawRenderPassQuad(const DrawingFrame* frame,
   shader->setLocalMatrix(content_mat);
   current_paint_.setShader(shader.get());
 
-  // TODO(ajuma): Remove this condition once general CSS filters are working
-  // correctly (http://crbug.com/160302), and add corresponding pixel tests.
-  if (quad->filters.HasReferenceFilter()) {
+  if (!quad->filters.IsEmpty()) {
     skia::RefPtr<SkImageFilter> filter = RenderSurfaceFilters::BuildImageFilter(
         quad->filters, content_texture->size());
+    // TODO(ajuma): Pass the quad's rect origin when applying the filter.

[ajuma, 2013/09/11 15:59:45]

This is why ImageFilterClipped pixel test doesn't pass with the software
renderer. We need something analogous to
https://chromiumcodereview.appspot.com/23060011. Thoughts on how to approach
this? 

[Stephen White, 2013/09/11 16:48:06]

It should just be a matter of getting the correct origin from
quad->rect.origin(), and applying that as a transform in current_canvas_. This
may require changing the draw call below from a drawRect() to a drawSprite(),
however, since we want the CTM to apply to the filter, but not to the
primitive's position. I suppose we could do a special case for filters here, and
early out. That would skip the mask code below, but I'm not sure filters + mask
does the correct thing in the existing code anyway -- TBD. The other option
would be to do a drawSprite() with only the filter applied, and then use the
resulting bitmap for the drawRect() call below. Then we could handle masks
correctly, I think.

[slavi, 2013/09/13 18:53:20]

AFAIK (I wrote the code) masks + filters do work correctly together with the
current code. I think there might be a layout test or two testing that.

[ajuma, 2013/10/15 19:36:20]

Done.

     if (filter)
       current_paint_.setImageFilter(filter.get());
   }