cc: Outset image rects by 1 for the purposes of the rtree.

cc/playback/discardable_image_map.cc

 // Copyright 2015 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/playback/discardable_image_map.h"
 
 #include <stddef.h>
 
 #include <algorithm>
 #include <limits>
@@ skipping 154 matching lines @@
         return false;
       *paint_bounds =
           current_paint->computeFastBounds(*paint_bounds, paint_bounds);
     }
 
     for (const auto& paint : base::Reversed(saved_paints_)) {
       if (!paint.canComputeFastBounds())
         return false;
       *paint_bounds = paint.computeFastBounds(*paint_bounds, paint_bounds);
     }
+
     return true;
   }
 
   void AddImage(sk_sp<const SkImage> image,
                 const SkRect& src_rect,
                 const SkRect& rect,
                 const SkMatrix& matrix,
                 const SkPaint* paint) {
     if (!image->isLazyGenerated())
       return;
@@ skipping 10 matching lines @@
 
     SkFilterQuality filter_quality = kNone_SkFilterQuality;
     if (paint) {
       filter_quality = paint->getFilterQuality();
     }
 
     SkIRect src_irect;
     src_rect.roundOut(&src_irect);
     gfx::Rect image_rect = SafeClampPaintRectToSize(paint_rect, canvas_size_);
 
+    // During raster, we use the device clip bounds on the canvas, which outsets
+    // the actual clip by 1 due to the possibility of antialiasing. Account for
+    // this here by outsetting the image rect by 1. Note that this only affects
+    // queries into the rtree, which will now return images that only touch the
+    // bounds of the query rect.
+    //
+    // Note that it's not sufficient for us to inset the device clip bounds at
+    // raster time, since we might be sending a larger-than-one-item display
+    // item to skia, which means that skia will internally determine whether to
+    // raster the picture (using device clip bounds that are outset).
+    image_rect.Inset(-1, -1);
+
     (*image_id_to_rect_)[image->uniqueID()].Union(image_rect);
     image_set_->push_back(std::make_pair(
         DrawImage(std::move(image), src_irect, filter_quality, matrix),
         image_rect));
   }
 
   // Currently this function only handles extracting images from SkImageShaders
   // embedded in SkPaints. Other embedded image cases, such as SkPictures,
   // are not yet handled.
   void AddPaintImage(const SkRect& rect, const SkPaint& paint) {
@@ skipping 59 matching lines @@
     DiscardableImageMap* image_map,
     const gfx::Size& bounds)
     : image_map_(image_map),
       metadata_canvas_(image_map->BeginGeneratingMetadata(bounds)) {}
 
 DiscardableImageMap::ScopedMetadataGenerator::~ScopedMetadataGenerator() {
   image_map_->EndGeneratingMetadata();
 }
 
 }  // namespace cc