cc: Move DamageTracker filter handling to MapRect.

While here, also fix a bug in which the rectangle in which the filter is
assumed to be visible was also mapped through the filter, and update unit
tests accordingly.

BUG=600821
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review-Url: https://codereview.chromium.org/2015343002
Cr-Commit-Position: refs/heads/master@{#397192}

cc/trees/damage_tracker.cc

@@ -29,23 +29,17 @@ DamageTracker::DamageTracker()
 
 DamageTracker::~DamageTracker() {}
 
-static inline void ExpandRectWithFilters(gfx::Rect* rect,
-                                         const FilterOperations& filters) {
-  int top, right, bottom, left;
-  filters.GetOutsets(&top, &right, &bottom, &left);
-  rect->Inset(-left, -top, -right, -bottom);
-}
-
 static inline void ExpandDamageRectInsideRectWithFilters(
     gfx::Rect* damage_rect,
     const gfx::Rect& pre_filter_rect,
     const FilterOperations& filters) {
-  gfx::Rect expanded_damage_rect = *damage_rect;
-  ExpandRectWithFilters(&expanded_damage_rect, filters);
-  gfx::Rect filter_rect = pre_filter_rect;
-  ExpandRectWithFilters(&filter_rect, filters);
+  // Compute the pixels in the background of the surface that could be affected
+  // by the damage in the content below.
+  gfx::Rect expanded_damage_rect = filters.MapRect(*damage_rect, SkMatrix::I());
+
+  // Restrict it to the rectangle in which the background filter is shown.
+  expanded_damage_rect.Intersect(pre_filter_rect);
 
-  expanded_damage_rect.Intersect(filter_rect);
   damage_rect->Union(expanded_damage_rect);
 }
 
@@ -144,8 +138,8 @@ void DamageTracker::UpdateDamageTrackingState(
     damage_rect_for_this_update = damage_from_active_layers;
     damage_rect_for_this_update.Union(damage_from_surface_mask);
     damage_rect_for_this_update.Union(damage_from_leftover_rects);
-
-    ExpandRectWithFilters(&damage_rect_for_this_update, filters);
+    damage_rect_for_this_update =
+        filters.MapRect(damage_rect_for_this_update, SkMatrix::I());
   }
 
   // Damage accumulates until we are notified that we actually did draw on that

cc/trees/damage_tracker_unittest.cc

@@ -703,7 +703,8 @@ TEST_F(DamageTrackerTest, VerifyDamageForBackgroundBlurredChild) {
 
   // CASE 1: Setting the update rect should cause the corresponding damage to
   //         the surface, blurred based on the size of the child's background
-  //         blur filter.
+  //         blur filter. Note that child1's render surface has a size of
+  //         206x208 due to contributions from grand_child1 and grand_child2.
   ClearDamageForAllSurfaces(root);
   root->SetUpdateRect(gfx::Rect(297, 297, 2, 2));
   root->layer_tree_impl()->property_trees()->needs_rebuild = true;
@@ -769,15 +770,12 @@ TEST_F(DamageTrackerTest, VerifyDamageForBackgroundBlurredChild) {
 
   root_damage_rect =
           root->render_surface()->damage_tracker()->current_damage_rect();
-  // Damage on the root should be: position of update_rect (99, 99), expanded by
-  // the blurring on child1, but since it is 1 pixel outside the layer, the
-  // expanding should be reduced by 1.
-  expected_damage_rect = gfx::Rect(99, 99, 1, 1);
-
-  expected_damage_rect.Inset(-outset_left + 1,
-                             -outset_top + 1,
-                             -outset_right,
-                             -outset_bottom);
+  // Damage on the root should be: the originally damaged rect (99,99 1x1)
+  // plus the rect that can influence with a 2px blur (93,93 13x13) intersected
+  // with the surface rect (100,100 206x208). So no additional damage occurs
+  // above or to the left, but there is additional damage within the blurred
+  // area.
+  expected_damage_rect = gfx::Rect(99, 99, 7, 7);
   EXPECT_EQ(expected_damage_rect.ToString(), root_damage_rect.ToString());
 
   // CASE 5: Setting the update rect on child2, which is above child1, will
@@ -807,12 +805,12 @@ TEST_F(DamageTrackerTest, VerifyDamageForBackgroundBlurredChild) {
           root->render_surface()->damage_tracker()->current_damage_rect();
   // Damage on child1 should be: position of update_rect offset by the child's
   // position (100, 100), and expanded by the damage.
-  expected_damage_rect = gfx::Rect(100, 100, 1, 1);
 
-  expected_damage_rect.Inset(-outset_left,
-                             -outset_top,
-                             -outset_right,
-                             -outset_bottom);
+  // Damage should be (0,0 1x1), offset by the 100,100 offset of child1 in
+  // root, and expanded 6px for the 2px blur (i.e., 94,94 13x13), but there
+  // should be no damage outside child1 (i.e. none above or to the left of
+  // 100,100.
+  expected_damage_rect = gfx::Rect(100, 100, 7, 7);
   EXPECT_EQ(expected_damage_rect.ToString(), root_damage_rect.ToString());
 }