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

cc/output/gl_renderer.cc

Index: cc/output/gl_renderer.cc
diff --git a/cc/output/gl_renderer.cc b/cc/output/gl_renderer.cc
index 12cac6e81e5816016178251d3469e59f212f217b..cfbb704baa5e9e79e77e458d188c09f9b51e8e7d 100644
--- a/cc/output/gl_renderer.cc
+++ b/cc/output/gl_renderer.cc
@@ -796,9 +796,8 @@ gfx::Rect GLRenderer::GetBackdropBoundingBoxForRenderPassQuad(
       contents_device_transform, scaled_region.BoundingBox()));
 
   if (ShouldApplyBackgroundFilters(quad)) {
-    int top, right, bottom, left;
-    quad->background_filters.GetOutsets(&top, &right, &bottom, &left);
-    backdrop_rect.Inset(-left, -top, -right, -bottom);
+    backdrop_rect =
+        quad->background_filters.MapRectReverse(backdrop_rect, SkMatrix::I());

[Stephen White, 2016/06/01 17:42:46]

If these are device-space rects, shouldn't we be using filters_scale here?

[jbroman, 2016/06/01 19:41:20]

I believe you're correct, which would make that an existing bug, as the
GetOutsets code didn't account for it either. Would you like that addressed in
this CL, or would a followup be good? (Or would you like such a fix to land
first?)

   }
 
   if (!backdrop_rect.IsEmpty() && use_aa) {