Move Ash-specific vector icon files into a separate directory

ui/gfx/BUILD.gn

Index: ui/gfx/BUILD.gn
diff --git a/ui/gfx/BUILD.gn b/ui/gfx/BUILD.gn
index 634c846373ac4787a9b73b706064db608f08f370..ae6aeb3e88a440438f64feeadcc506f91e2b0ce7 100644
--- a/ui/gfx/BUILD.gn
+++ b/ui/gfx/BUILD.gn
@@ -423,6 +423,9 @@ action("aggregate_vector_icons") {
   script = "vector_icons/aggregate_vector_icons.py"
 
   inputs = vector_icons_sources_gypi.common
+  if (use_ash || is_chromeos) {
+    inputs += vector_icons_sources_gypi.ash
+  }
 
   outputs = [
     vector_icons_cc_file,
@@ -500,6 +503,7 @@ group("memory_buffer") {
     ]
   }
 }
+
 # Cannot be a static_library in component builds due to exported functions
 source_set("memory_buffer_sources") {
   visibility = [ ":*" ]  # Depend on through ":memory_buffer".