diff --git a/src/gpu/GrSamplePatternDictionary.cpp b/src/gpu/GrSamplePatternDictionary.cpp
new file mode 100644
index 0000000..453ed45
--- /dev/null
+++ b/src/gpu/GrSamplePatternDictionary.cpp
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2019 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrSamplePatternDictionary.h"
+
+bool GrSamplePatternDictionary::LessThan::operator()(
+        const SkTArray<SkPoint>& a, const SkTArray<SkPoint>& b) const {
+    if (a.count() != b.count()) {
+        return a.count() < b.count();
+    }
+    for (int i = 0; i < a.count(); ++i) {
+        // This doesn't have geometric meaning. We just need to define an ordering for std::map.
+        if (a[i].x() != b[i].x()) {
+            return a[i].x() < b[i].x();
+        }
+        if (a[i].y() != b[i].y()) {
+            return a[i].y() < b[i].y();
+        }
+    }
+    return false;  // Both sample patterns are equal, therefore, "a < b" is false.
+}
+
+int GrSamplePatternDictionary::findOrAssignSamplePatternKey(
+        const SkTArray<SkPoint>& sampleLocations) {
+    if (std::numeric_limits<int>::max() == fSampleLocationsArray.count()) {
+        return 0;
+    }
+    const auto& insertResult = fSamplePatternKeyMap.insert(
+            {sampleLocations, fSampleLocationsArray.count()});
+    if (insertResult.second) {
+        // This means the "insert" call did not find the pattern in the key map already, and
+        // therefore an actual insertion took place. (We don't expect to see many unique sample
+        // patterns.)
+        const SkTArray<SkPoint>& sampleLocations = insertResult.first->first;
+        fSampleLocationsArray.push_back(&sampleLocations);
+    }
+    return insertResult.first->second;  // Return the new sample pattern key.
+}