Implement filter primitive subregion for reference CSS filters. This required refactoring determin…

Source/core/platform/graphics/filters/FilterOperations.cpp

Index: Source/core/platform/graphics/filters/FilterOperations.cpp
diff --git a/Source/core/platform/graphics/filters/FilterOperations.cpp b/Source/core/platform/graphics/filters/FilterOperations.cpp
index 28ac9f7f1a1a6df3578fb2ba9e053a125fe8d1d5..870148231d4fc1197d8d4be0f5068f6336c7cb6a 100644
--- a/Source/core/platform/graphics/filters/FilterOperations.cpp
+++ b/Source/core/platform/graphics/filters/FilterOperations.cpp
@@ -108,7 +108,7 @@ bool FilterOperations::hasOutsets() const
 {
     for (size_t i = 0; i < m_operations.size(); ++i) {
         FilterOperation::OperationType operationType = m_operations.at(i).get()->getOperationType();
-        if (operationType == FilterOperation::BLUR || operationType == FilterOperation::DROP_SHADOW)
+        if (operationType == FilterOperation::BLUR || operationType == FilterOperation::DROP_SHADOW || operationType == FilterOperation::REFERENCE)
             return true;
     }
     return false;
@@ -140,6 +140,21 @@ FilterOutsets FilterOperations::outsets() const
             totalOutsets += outsets;
             break;
         }
+        case FilterOperation::REFERENCE: {
+            ReferenceFilterOperation* referenceOperation = static_cast<ReferenceFilterOperation*>(filterOperation);
+            if (referenceOperation->filterEffect()) {
+                FloatRect outsetRect(0, 0, 1, 1);
+                outsetRect = referenceOperation->filterEffect()->mapRectRecursive(outsetRect);
+                FilterOutsets outsets(
+                    std::max(0.0f, -outsetRect.y()),
+                    std::max(0.0f, outsetRect.x() + outsetRect.width() - 1),
+                    std::max(0.0f, outsetRect.y() + outsetRect.height() - 1),
+                    std::max(0.0f, -outsetRect.x())
+                );
+                totalOutsets += outsets;
+            }
+            break;
+        }
         case FilterOperation::CUSTOM:
         case FilterOperation::VALIDATED_CUSTOM: {
             // FIXME: Need to include the filter margins here.