Revert "cc: Move canvas clear from picture to picture_pile_impl"

cc/resources/picture_pile_impl.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 <algorithm>
 #include <limits>
 
 #include "base/debug/trace_event.h"
 #include "cc/base/region.h"
 #include "cc/debug/debug_colors.h"
@@ skipping 78 matching lines @@
 
   canvas->save();
   canvas->translate(-canvas_rect.x(), -canvas_rect.y());
 
   gfx::SizeF total_content_size = gfx::ScaleSize(tiling_.total_size(),
                                                  contents_scale);
   gfx::Rect total_content_rect(gfx::ToCeiledSize(total_content_size));
   gfx::Rect content_rect = total_content_rect;
   content_rect.Intersect(canvas_rect);
 
-  // Clear an inflated content rect, to ensure that we always sample
-  // a correct pixel.
-  gfx::Rect inflated_content_rect = total_content_rect;
-  inflated_content_rect.Inset(0, 0, -1, -1);
+  // Clear one texel inside the right/bottom edge of the content rect,
+  // as it may only be partially covered by the picture playback.
+  // Also clear one texel outside the right/bottom edge of the content rect,
+  // as it may get blended in by linear filtering when zoomed in.
+  gfx::Rect deflated_content_rect = total_content_rect;
+  deflated_content_rect.Inset(0, 0, 1, 1);
 
-  SkPaint background_paint;
-  background_paint.setColor(background_color_);
-  background_paint.setXfermodeMode(SkXfermode::kSrc_Mode);
-  canvas->drawRect(RectToSkRect(inflated_content_rect), background_paint);
+  gfx::Rect canvas_outside_content_rect = canvas_rect;
+  canvas_outside_content_rect.Subtract(deflated_content_rect);
+
+  if (!canvas_outside_content_rect.IsEmpty()) {
+    gfx::Rect inflated_content_rect = total_content_rect;
+    inflated_content_rect.Inset(0, 0, -1, -1);
+    canvas->clipRect(gfx::RectToSkRect(inflated_content_rect),
+                     SkRegion::kReplace_Op);
+    canvas->clipRect(gfx::RectToSkRect(deflated_content_rect),
+                     SkRegion::kDifference_Op);
+    canvas->drawColor(background_color_, SkXfermode::kSrc_Mode);
+  }
 
   // Rasterize the collection of relevant picture piles.
   gfx::Rect layer_rect = gfx::ToEnclosingRect(
       gfx::ScaleRect(content_rect, 1.f / contents_scale));
 
   canvas->clipRect(gfx::RectToSkRect(content_rect),
                    SkRegion::kReplace_Op);
   Region unclipped(content_rect);
 
   if (raster_stats) {
@@ skipping 200 matching lines @@
           layer_rect_,
           *picture_list_iterator_);
       if (pixel_ref_iterator_)
         return;
     }
     ++tile_iterator_;
   } while (AdvanceToTileWithPictures());
 }
 
 }  // namespace cc