Add packages to optimize svgs dynamically

These packages will be used to dynamically optimize SVG images
during the build.

R=jacktfranklin@chromium.org

Bug: 1216402
Change-Id: I04e95aa7d79c9d67beaf8a7861182c52b16b7d0f
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/2939992
Reviewed-by: Jack Franklin <jacktfranklin@chromium.org>
Commit-Queue: Tim van der Lippe <tvanderlippe@chromium.org>
diff --git a/node_modules/csso/lib/replace/index.js b/node_modules/csso/lib/replace/index.js
new file mode 100644
index 0000000..2e2c5f6
--- /dev/null
+++ b/node_modules/csso/lib/replace/index.js
@@ -0,0 +1,24 @@
+var walk = require('css-tree').walk;
+var handlers = {
+    Atrule: require('./Atrule'),
+    AttributeSelector: require('./AttributeSelector'),
+    Value: require('./Value'),
+    Dimension: require('./Dimension'),
+    Percentage: require('./Percentage'),
+    Number: require('./Number'),
+    String: require('./String'),
+    Url: require('./Url'),
+    Hash: require('./color').compressHex,
+    Identifier: require('./color').compressIdent,
+    Function: require('./color').compressFunction
+};
+
+module.exports = function(ast) {
+    walk(ast, {
+        leave: function(node, item, list) {
+            if (handlers.hasOwnProperty(node.type)) {
+                handlers[node.type].call(this, node, item, list);
+            }
+        }
+    });
+};