FIX: add support for style element in SVGs

lib/upload_creator.rb

@@ -9,7 +9,7 @@ class UploadCreator
 
   WHITELISTED_SVG_ELEMENTS ||= %w{
     circle clippath defs ellipse g line linearGradient path polygon polyline
-    radialGradient rect stop svg text textpath tref tspan use
+    radialGradient rect stop style svg text textpath tref tspan use
   }.each(&:freeze)
 
   # Available options

spec/fixtures/images/image.svg

@@ -1,3 +1,6 @@
 <svg width="100" height="50">
-  <text x="25" y="25">Discourse</text>
+  <style>
+    .black { fill: #FFFFFF; }
+  </style>
+  <text class="black" x="25" y="25">Discourse</text>
 </svg>

spec/models/upload_spec.rb

@@ -45,6 +45,16 @@ describe Upload do
     end
   end
 
+  it "supports <style> element in SVG" do
+    SiteSetting.authorized_extensions = "svg"
+
+    upload = UploadCreator.new(image_svg, image_svg_filename).create_for(user_id)
+    expect(upload.valid?).to eq(true)
+
+    path = Discourse.store.path_for(upload)
+    expect(File.read(path)).to match(/<style>/)
+  end
+
   it "can reconstruct dimensions on demand" do
     upload = UploadCreator.new(huge_image, "image.png").create_for(user_id)