Generate web, devtools files into their own sub-dirs.

Source/web/BUILD.gn

Index: Source/web/BUILD.gn
diff --git a/Source/web/BUILD.gn b/Source/web/BUILD.gn
index e26a587a1d3b7052d101e3d31ee251d623c495c6..db1211c36ba3bd6e68208413689f8341407dc5a5 100644
--- a/Source/web/BUILD.gn
+++ b/Source/web/BUILD.gn
@@ -115,7 +115,7 @@ make_file_arrays("picker_common") {
     "resources/pickerCommon.css",
     "resources/pickerCommon.js",
   ]
-  filename = "PickerCommon"
+  filename = "web/PickerCommon"
 }
 
 make_file_arrays("color_suggestion_picker") {
@@ -123,7 +123,7 @@ make_file_arrays("color_suggestion_picker") {
     "resources/colorSuggestionPicker.css",
     "resources/colorSuggestionPicker.js",
   ]
-  filename = "ColorSuggestionPicker"
+  filename = "web/ColorSuggestionPicker"
 }
 
 make_file_arrays("calendar_picker") {
@@ -134,5 +134,5 @@ make_file_arrays("calendar_picker") {
     "resources/suggestionPicker.css",
     "resources/suggestionPicker.js",
   ]
-  filename = "CalendarPicker"
+  filename = "web/CalendarPicker"
 }