cc: use Skia's filterBounds() traversal, not computeFastBounds().

cc/output/gl_renderer.cc

 // Copyright 2010 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/gl_renderer.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 970 matching lines @@
         cf = skia::AdoptRef(colorfilter_rawptr);
       }
 
       if (cf && cf->asColorMatrix(color_matrix) && !filter->getInput(0)) {
         // We have a single color matrix as a filter; apply it locally
         // in the compositor.
         use_color_matrix = true;
       } else {
         gfx::RectF src_rect = rect;
         gfx::Vector2dF scale = quad->filters_scale;
-        // Compute the destination rect for the filtered output.
-        // Note that we leave the dest rect equal to the src rect when
-        // a filter chain cannot compute its bounds. This is correct
-        // behaviour, but Skia is a little conservative at the moment.
-        // Once Skia makes the fast-bounds traversal crop-rect aware
-        // (http://skbug.com/4627), this won't be a problem
-        // for Chrome since Blink always sets a crop rect on the leaf nodes
-        // of the DAG, making it always computable.
-        // TODO(senorblanco): remove this comment when http://skbug.com/4627
-        // is fixed.
-        if (filter->canComputeFastBounds()) {
-          SkRect result_rect;
-          rect.Scale(1.0f / scale.x(), 1.0f / scale.y());
-          filter->computeFastBounds(gfx::RectFToSkRect(rect), &result_rect);
-          rect = gfx::SkRectToRectF(result_rect);
-          rect.Scale(scale.x(), scale.y());
-        }
+        SkMatrix scale_matrix;
+        scale_matrix.setScale(scale.x(), scale.y());
+        SkIRect result_rect;
+        filter->filterBounds(gfx::RectToSkIRect(quad->rect), scale_matrix,
+                             &result_rect,
+                             SkImageFilter::kForward_MapDirection);
+        rect = gfx::SkRectToRectF(SkRect::Make(result_rect));
         filter_image = ApplyImageFilter(ScopedUseGrContext::Create(this, frame),
                                         resource_provider_, src_rect, rect,
                                         scale, filter.get(), contents_texture);
         if (filter_image) {
           filter_image_id = filter_image->getTextureHandle(true);
           DCHECK(filter_image_id);
         }
       }
     }
   }
@@ skipping 2589 matching lines @@
       texture_id = pending_overlay_resources_.back()->texture_id();
     }
 
     context_support_->ScheduleOverlayPlane(
         overlay.plane_z_order, overlay.transform, texture_id,
         ToNearestRect(overlay.display_rect), overlay.uv_rect);
   }
 }
 
 }  // namespace cc