[SVGDom] Initial linear gradient support

BUILD.gn

 # Copyright 2016 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//gn/shared_sources.gni")
 
 declare_args() {
   skia_enable_tools = !is_fuchsia && !is_component_build
 
@@ skipping 704 matching lines @@
   test_lib("experimental_svg_model") {
     public_include_dirs = [ "experimental/svg/model" ]
     sources = [
       "experimental/svg/model/SkSVGAttribute.cpp",
       "experimental/svg/model/SkSVGAttributeParser.cpp",
       "experimental/svg/model/SkSVGCircle.cpp",
       "experimental/svg/model/SkSVGContainer.cpp",
       "experimental/svg/model/SkSVGDOM.cpp",
       "experimental/svg/model/SkSVGEllipse.cpp",
       "experimental/svg/model/SkSVGLine.cpp",
+      "experimental/svg/model/SkSVGLinearGradient.cpp",
       "experimental/svg/model/SkSVGNode.cpp",
       "experimental/svg/model/SkSVGPath.cpp",
       "experimental/svg/model/SkSVGPoly.cpp",
       "experimental/svg/model/SkSVGRect.cpp",
       "experimental/svg/model/SkSVGRenderContext.cpp",
       "experimental/svg/model/SkSVGSVG.cpp",
       "experimental/svg/model/SkSVGShape.cpp",
+      "experimental/svg/model/SkSVGStop.cpp",
       "experimental/svg/model/SkSVGTransformableNode.cpp",
       "experimental/svg/model/SkSVGValue.cpp",
     ]
     deps = [
       ":skia",
     ]
   }
 
   executable("dm") {
     sources = [
@@ skipping 60 matching lines @@
     sources = [
       "tools/SkShaper_primitive.cpp",
       "tools/using_skia_and_harfbuzz.cpp",
     ]
     deps = [
       ":skia",
     ]
     testonly = true
   }
 }