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

cc/output/filter_operations_unittest.cc

Index: cc/output/filter_operations_unittest.cc
diff --git a/cc/output/filter_operations_unittest.cc b/cc/output/filter_operations_unittest.cc
index 64c127c29f2891c032efc6be41fa6045b1f2da25..aaf40b90fe519cacaae0a3b27ab73959331d9b1f 100644
--- a/cc/output/filter_operations_unittest.cc
+++ b/cc/output/filter_operations_unittest.cc
@@ -34,6 +34,13 @@ TEST(FilterOperationsTest, MapRectBlur) {
             ops.MapRect(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
 }
 
+TEST(FilterOperationsTest, MapRectReverseBlur) {
+  FilterOperations ops;
+  ops.Append(FilterOperation::CreateBlurFilter(20));
+  EXPECT_EQ(gfx::Rect(-60, -60, 130, 130),
+            ops.MapRectReverse(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
+}
+
 TEST(FilterOperationsTest, GetOutsetsDropShadowReferenceFilter) {
   // TODO(hendrikw): We need to make outsets for reference filters be in line
   // with non-reference filters. See crbug.com/523534
@@ -66,6 +73,18 @@ TEST(FilterOperationsTest, MapRectDropShadowReferenceFilter) {
             ops.MapRect(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
 }
 
+TEST(FilterOperationsTest, MapRectReverseDropShadowReferenceFilter) {
+  FilterOperations ops;
+  ops.Append(
+      FilterOperation::CreateReferenceFilter(SkDropShadowImageFilter::Make(
+          SkIntToScalar(3), SkIntToScalar(8), SkIntToScalar(4),
+          SkIntToScalar(9), SK_ColorBLACK,
+          SkDropShadowImageFilter::kDrawShadowAndForeground_ShadowMode,
+          nullptr)));
+  EXPECT_EQ(gfx::Rect(-15, -35, 34, 64),
+            ops.MapRectReverse(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
+}
+
 TEST(FilterOperationsTest, MapRectOffsetReferenceFilter) {
   sk_sp<SkImageFilter> filter = SkOffsetImageFilter::Make(30, 40, nullptr);
   FilterOperations ops;
@@ -74,6 +93,14 @@ TEST(FilterOperationsTest, MapRectOffsetReferenceFilter) {
             ops.MapRect(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
 }
 
+TEST(FilterOperationsTest, MapRectReverseOffsetReferenceFilter) {
+  sk_sp<SkImageFilter> filter = SkOffsetImageFilter::Make(30, 40, nullptr);
+  FilterOperations ops;
+  ops.Append(FilterOperation::CreateReferenceFilter(std::move(filter)));
+  EXPECT_EQ(gfx::Rect(-30, -40, 10, 10),
+            ops.MapRectReverse(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
+}
+
 TEST(FilterOperationsTest, GetOutsetsNullReferenceFilter) {
   FilterOperations ops;
   ops.Append(FilterOperation::CreateReferenceFilter(nullptr));
@@ -94,6 +121,13 @@ TEST(FilterOperationsTest, MapRectNullReferenceFilter) {
             ops.MapRect(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
 }
 
+TEST(FilterOperationsTest, MapRectReverseNullReferenceFilter) {
+  FilterOperations ops;
+  ops.Append(FilterOperation::CreateReferenceFilter(nullptr));
+  EXPECT_EQ(gfx::Rect(0, 0, 10, 10),
+            ops.MapRectReverse(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
+}
+
 TEST(FilterOperationsTest, GetOutsetsDropShadow) {
   FilterOperations ops;
   ops.Append(FilterOperation::CreateDropShadowFilter(gfx::Point(3, 8), 20, 0));
@@ -113,6 +147,13 @@ TEST(FilterOperationsTest, MapRectDropShadow) {
             ops.MapRect(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
 }
 
+TEST(FilterOperationsTest, MapRectReverseDropShadow) {
+  FilterOperations ops;
+  ops.Append(FilterOperation::CreateDropShadowFilter(gfx::Point(3, 8), 20, 0));
+  EXPECT_EQ(gfx::Rect(-63, -68, 130, 130),
+            ops.MapRectReverse(gfx::Rect(0, 0, 10, 10), SkMatrix::I()));
+}
+
 #define SAVE_RESTORE_AMOUNT(filter_name, filter_type, a)                  \
   {                                                                       \
     FilterOperation op = FilterOperation::Create##filter_name##Filter(a); \