cc: Implement and use FilterOperations::MapRectReverse for mapping backdrop bounding box.

cc/output/filter_operation.cc

 // Copyright 2013 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 <stddef.h>
 
 #include <algorithm>
 
 #include "base/trace_event/trace_event_argument.h"
 #include "base/values.h"
@@ skipping 334 matching lines @@
       SkIRect in_rect = gfx::RectToSkIRect(rect);
       SkIRect out_rect = image_filter()->filterBounds(
           in_rect, matrix, SkImageFilter::kForward_MapDirection);
       return gfx::SkIRectToRect(out_rect);
     }
     default:
       return rect;
   }
 }
 
+gfx::Rect FilterOperation::MapRectReverse(const gfx::Rect& rect,
+                                          const SkMatrix& matrix) const {
+  switch (type_) {
+    case FilterOperation::BLUR: {
+      SkVector spread = MapStdDeviation(amount(), matrix);
+      gfx::Rect result = rect;
+      result.Inset(-spread.x(), -spread.y(), -spread.x(), -spread.y());
+      return result;
+    }
+    case FilterOperation::DROP_SHADOW: {
+      SkVector spread = MapStdDeviation(amount(), matrix);
+      gfx::Rect result = rect;
+      result.Inset(-spread.x(), -spread.y(), -spread.x(), -spread.y());
+      result -= drop_shadow_offset().OffsetFromOrigin();
+      result.Union(rect);
+      return result;
+    }
+    case FilterOperation::REFERENCE: {
+      if (!image_filter())
+        return rect;
+      SkIRect in_rect = gfx::RectToSkIRect(rect);
+      SkIRect out_rect = image_filter()->filterBounds(
+          in_rect, matrix, SkImageFilter::kReverse_MapDirection);
+      return gfx::SkIRectToRect(out_rect);
+    }
+    default:
+      return rect;
+  }
+}
+
 }  // namespace cc