Scale the ALPHA_THRESHOLD filter's region based on the device scale factor.

cc/output/software_renderer.cc

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/output/software_renderer.h"
 
 #include "base/debug/trace_event.h"
 #include "cc/base/math_util.h"
 #include "cc/output/compositor_frame.h"
 #include "cc/output/compositor_frame_ack.h"
@@ skipping 505 matching lines @@
 
   SkMatrix content_mat;
   content_mat.setRectToRect(content_rect, dest_rect,
                             SkMatrix::kFill_ScaleToFit);
 
   const SkBitmap* content = lock.sk_bitmap();
 
   SkBitmap filter_bitmap;
   if (!quad->filters.IsEmpty()) {
     skia::RefPtr<SkImageFilter> filter = RenderSurfaceFilters::BuildImageFilter(
-        quad->filters, content_texture->size());
+        quad->filters, quad->scale, content_texture->size());
     // TODO(ajuma): In addition origin translation, the canvas should also be
     // scaled to accomodate device pixel ratio and pinch zoom. See
     // crbug.com/281516 and crbug.com/281518.
     // TODO(ajuma): Apply the filter in the same pass as the content where
     // possible (e.g. when there's no origin offset). See crbug.com/308201.
     if (filter) {
       SkImageInfo info = SkImageInfo::MakeN32Premul(
           content_texture->size().width(), content_texture->size().height());
       if (filter_bitmap.allocPixels(info)) {
         SkCanvas canvas(filter_bitmap);
@@ skipping 107 matching lines @@
 }
 
 void SoftwareRenderer::DidChangeVisibility() {
   if (visible())
     EnsureBackbuffer();
   else
     DiscardBackbuffer();
 }
 
 }  // namespace cc