Add support for converting cc::FilterOperations into an SkImageFilter

cc/output/filter_operations.cc

Index: cc/output/filter_operations.cc
diff --git a/cc/output/filter_operations.cc b/cc/output/filter_operations.cc
index e526f5c419bed3ae53cbab223109f19c85ec385b..92ddd684777ef9e71fab6cbd1a3805a0f0db3dd9 100644
--- a/cc/output/filter_operations.cc
+++ b/cc/output/filter_operations.cc
@@ -59,7 +59,10 @@ void FilterOperations::GetOutsets(int* top,
                                   int* left) const {
   *top = *right = *bottom = *left = 0;
   for (size_t i = 0; i < operations_.size(); ++i) {
-    const FilterOperation op = operations_[i];
+    const FilterOperation& op = operations_[i];
+    // TODO(ajuma): Add support for reference filters once SkImageFilter
+    // reports its outsets.
+    DCHECK(op.type() != FilterOperation::REFERENCE);
     if (op.type() == FilterOperation::BLUR ||
         op.type() == FilterOperation::DROP_SHADOW) {
       int spread = SpreadForStdDeviation(op.amount());
@@ -80,11 +83,14 @@ void FilterOperations::GetOutsets(int* top,
 
 bool FilterOperations::HasFilterThatMovesPixels() const {
   for (size_t i = 0; i < operations_.size(); ++i) {
-    const FilterOperation op = operations_[i];
+    const FilterOperation& op = operations_[i];
+    // TODO(ajuma): Once SkImageFilter reports its outsets, use those here to
+    // determine whether a reference filter really moves pixels.
     switch (op.type()) {
       case FilterOperation::BLUR:
       case FilterOperation::DROP_SHADOW:
       case FilterOperation::ZOOM:
+      case FilterOperation::REFERENCE:
         return true;
       case FilterOperation::OPACITY:
       case FilterOperation::COLOR_MATRIX:
@@ -104,12 +110,15 @@ bool FilterOperations::HasFilterThatMovesPixels() const {
 
 bool FilterOperations::HasFilterThatAffectsOpacity() const {
   for (size_t i = 0; i < operations_.size(); ++i) {
-    const FilterOperation op = operations_[i];
+    const FilterOperation& op = operations_[i];
+    // TODO(ajuma): Make this smarter for reference filters. Once SkImageFilter
+    // can report affectsOpacity(), call that.
     switch (op.type()) {
       case FilterOperation::OPACITY:
       case FilterOperation::BLUR:
       case FilterOperation::DROP_SHADOW:
       case FilterOperation::ZOOM:
+      case FilterOperation::REFERENCE:
         return true;
       case FilterOperation::COLOR_MATRIX: {
         const SkScalar* matrix = op.matrix();
@@ -135,6 +144,14 @@ bool FilterOperations::HasFilterThatAffectsOpacity() const {
   return false;
 }
 
+bool FilterOperations::HasReferenceFilter() const {
+  for (size_t i = 0; i < operations_.size(); ++i) {
+    if (operations_[i].type() == FilterOperation::REFERENCE)
+      return true;
+  }
+  return false;
+}
+
 FilterOperations FilterOperations::Blend(const FilterOperations& from,
                                          double progress) const {
   FilterOperations blended_filters;