Update filter blending to match spec draft.

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 92ddd684777ef9e71fab6cbd1a3805a0f0db3dd9..afea8eb714a05aebd5ed33aa9fcee362e3361a8c 100644
--- a/cc/output/filter_operations.cc
+++ b/cc/output/filter_operations.cc
@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include <algorithm>
 #include <cmath>
 
 #include "cc/output/filter_operations.h"
@@ -154,6 +155,9 @@ bool FilterOperations::HasReferenceFilter() const {
 
 FilterOperations FilterOperations::Blend(const FilterOperations& from,
                                          double progress) const {
+  if (HasReferenceFilter() || from.HasReferenceFilter())
+    return *this;
+
   FilterOperations blended_filters;
   if (from.size() == 0) {
     for (size_t i = 0; i < size(); i++)
@@ -170,7 +174,7 @@ FilterOperations FilterOperations::Blend(const FilterOperations& from,
   }
 
   if (from.size() != size())
-    return *this;
+    return BlendRaggedOperations(from, progress);

[ajuma, 2013/11/11 18:39:41]

Could we merge the logic of blending different sized lists with that for
blending lists of the same size? (Since same-size lists can be viewed as just a
special case of lists whose sizes don't necessarily match.)

[avallee, 2013/11/12 20:18:09]

Done.

 
   for (size_t i = 0; i < size(); i++) {
     if (from.at(i).type() != at(i).type())
@@ -192,4 +196,36 @@ scoped_ptr<base::Value> FilterOperations::AsValue() const {
   return value.PassAs<base::Value>();
 }
 
+FilterOperations FilterOperations::BlendRaggedOperations(
+    const FilterOperations& from,
+    double progress) const {
+  size_t shorter_size = std::min(from.size(), size());
+  for (size_t i = 0; i < shorter_size; ++i) {
+    if (from.at(i).type() != at(i).type())
+      return *this;
+  }
+
+  FilterOperations blended_filters;
+  for (size_t i = 0; i < shorter_size; ++i) {
+    blended_filters.Append(
+        FilterOperation::Blend(&from.at(i), &at(i), progress));
+  }
+
+  bool from_is_longer = size() < from.size();
+
+  if (from_is_longer) {
+    for (size_t i = shorter_size; i < from.size(); ++i) {
+      blended_filters.Append(
+          FilterOperation::Blend(&from.at(i), NULL, progress));
+    }
+  } else {
+    for (size_t i = shorter_size; i < size(); ++i) {
+      blended_filters.Append(
+          FilterOperation::Blend(NULL, &at(i), progress));
+    }
+  }
+
+  return blended_filters;
+}
+
 }  // namespace cc