Implement -webkit-box-reflect as a filter.

third_party/WebKit/Source/platform/graphics/filters/FilterOperations.cpp

Index: third_party/WebKit/Source/platform/graphics/filters/FilterOperations.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/filters/FilterOperations.cpp b/third_party/WebKit/Source/platform/graphics/filters/FilterOperations.cpp
index e1db93e02c09374d4d28f361a044be76435c7f56..093ddf931b64863739cf33d5023ece1764267e5d 100644
--- a/third_party/WebKit/Source/platform/graphics/filters/FilterOperations.cpp
+++ b/third_party/WebKit/Source/platform/graphics/filters/FilterOperations.cpp
@@ -105,7 +105,10 @@ bool FilterOperations::hasOutsets() const
 {
     for (size_t i = 0; i < m_operations.size(); ++i) {
         FilterOperation::OperationType operationType = m_operations.at(i)->type();
-        if (operationType == FilterOperation::BLUR || operationType == FilterOperation::DROP_SHADOW || operationType == FilterOperation::REFERENCE)
+        if (operationType == FilterOperation::BLUR
+            || operationType == FilterOperation::DROP_SHADOW
+            || operationType == FilterOperation::REFERENCE
+            || operationType == FilterOperation::BOX_REFLECT)
             return true;
     }
     return false;
@@ -152,6 +155,10 @@ FilterOutsets FilterOperations::outsets() const
             }
             break;
         }
+        case FilterOperation::BOX_REFLECT: {
+            // Already accounted for at all call sites.

[Stephen White, 2016/03/30 14:41:35]

This seems fragile to callers expecting that box-reflect will behave like other
filters.

If it's not possible to express box-filter's behaviour as outsets, I think it's
finally time to convert from outsets to a rect-mapping function as Skia does
internally (see
https://bugs.chromium.org/p/chromium/issues/detail?id=523534#c2). This will
require some refactoring in Blink, but I'd very much prefer that we do that
first.

+            break;
+        }
         default:
             break;
         }
@@ -176,4 +183,3 @@ bool FilterOperations::hasFilterThatMovesPixels() const
 }
 
 } // namespace blink
-