Add Paths as first-class types in configs.

scripts/slave/recipe_modules/chromium/config.expected/Release-win.intel.64-to-win.intel.32.json

 {
   "android_defaults": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "default_targets": [
         "All"
       ]
     }, 
     "gyp_env": {
       "GYP_CROSSCOMPILE": "1", 
-      "GYP_DEFINES": "OS=android component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=['orderfiles', 'orderfile.out'] target_arch=arm", 
+      "GYP_DEFINES": "OS=android component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=Path([CHECKOUT], ('orderfiles', 'orderfile.out')) target_arch=arm", 
       "GYP_GENERATORS": "ninja", 
       "GYP_GENERATOR_FLAGS": "default_target=All", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "blink": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma", 
       "default_targets": [
         "all_webkit"
       ]
     }, 
     "gyp_env": {
       "GYP_DEFINES": "chromium_win_pch=0 component=static_library fastbuild=1 use_ash=0 use_aura=0", 
       "GYP_GENERATORS": "ninja", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "chromium": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma", 
       "default_targets": [
         "All", 
         "chromium_builder_tests"
       ]
     }, 
     "gyp_env": {
       "GYP_DEFINES": "chromium_win_pch=0 component=static_library fastbuild=1", 
       "GYP_GENERATORS": "ninja", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "clang_builder": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma-clang", 
       "default_targets": [
         "All"
       ]
     }, 
     "gyp_env": {
       "GYP_CROSSCOMPILE": "1", 
-      "GYP_DEFINES": "OS=android chromium_win_pch=0 clang=1 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=['orderfiles', 'orderfile.out'] target_arch=arm", 
+      "GYP_DEFINES": "OS=android chromium_win_pch=0 clang=1 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=Path([CHECKOUT], ('orderfiles', 'orderfile.out')) target_arch=arm", 
       "GYP_GENERATORS": "ninja", 
       "GYP_GENERATOR_FLAGS": "default_target=All", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "component_builder": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma", 
       "default_targets": [
         "All"
       ]
     }, 
     "gyp_env": {
       "GYP_CROSSCOMPILE": "1", 
-      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=shared_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=['orderfiles', 'orderfile.out'] target_arch=arm", 
+      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=shared_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=Path([CHECKOUT], ('orderfiles', 'orderfile.out')) target_arch=arm", 
       "GYP_GENERATORS": "ninja", 
       "GYP_GENERATOR_FLAGS": "default_target=All", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "klp_builder": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma", 
       "default_targets": [
         "All"
       ]
     }, 
     "gyp_env": {
       "GYP_CROSSCOMPILE": "1", 
-      "GYP_DEFINES": "OS=android android_sdk_root=['third_party', 'android_tools_internal', 'sdk'] android_sdk_version=KeyLimePie chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=['orderfiles', 'orderfile.out'] target_arch=arm", 
+      "GYP_DEFINES": "OS=android android_sdk_root=Path([CHECKOUT], ('third_party', 'android_tools_internal', 'sdk')) android_sdk_version=KeyLimePie chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=Path([CHECKOUT], ('orderfiles', 'orderfile.out')) target_arch=arm", 
       "GYP_GENERATORS": "ninja", 
       "GYP_GENERATOR_FLAGS": "default_target=All", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "main_builder": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma", 
       "default_targets": [
         "All"
       ]
     }, 
     "gyp_env": {
       "GYP_CROSSCOMPILE": "1", 
-      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=['orderfiles', 'orderfile.out'] target_arch=arm", 
+      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=Path([CHECKOUT], ('orderfiles', 'orderfile.out')) target_arch=arm", 
       "GYP_GENERATORS": "ninja", 
       "GYP_GENERATOR_FLAGS": "default_target=All", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "msvs": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('build',))", 
     "compile_py": {
       "build_tool": "msvs"
     }, 
     "gyp_env": {
       "GYP_DEFINES": "component=static_library", 
       "GYP_GENERATORS": "msvs", 
       "GYP_GENERATOR_FLAGS": "msvs_error_on_missing_sources=1", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "ninja": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja"
     }, 
     "gyp_env": {
       "GYP_DEFINES": "component=static_library", 
       "GYP_GENERATORS": "ninja", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "try_builder": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma", 
       "default_targets": [
         "All"
       ]
     }, 
     "gyp_env": {
       "GYP_CROSSCOMPILE": "1", 
-      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=['orderfiles', 'orderfile.out'] target_arch=arm", 
+      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=Path([CHECKOUT], ('orderfiles', 'orderfile.out')) target_arch=arm", 
       "GYP_GENERATORS": "ninja", 
       "GYP_GENERATOR_FLAGS": "default_target=All", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "v8": {
     "build_config_fs": "Release", 
-    "build_dir": "", 
+    "build_dir": "Path([CHECKOUT], ())", 
     "compile_py": {
       "build_tool": "make", 
       "default_targets": [
         "buildbot"
       ]
     }, 
     "gyp_env": {
       "GYP_DEFINES": "v8_target_arch=ia32", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "x86_builder": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma", 
       "default_targets": [
         "All"
       ]
     }, 
     "gyp_env": {
       "GYP_CROSSCOMPILE": "1", 
-      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=['orderfiles', 'orderfile.out'] target_arch=ia32", 
+      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=Path([CHECKOUT], ('orderfiles', 'orderfile.out')) target_arch=ia32", 
       "GYP_GENERATORS": "ninja", 
       "GYP_GENERATOR_FLAGS": "default_target=All", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "x86_try_builder": {
     "build_config_fs": "Release", 
-    "build_dir": "out", 
+    "build_dir": "Path([CHECKOUT], ('out',))", 
     "compile_py": {
       "build_tool": "ninja", 
       "compiler": "goma", 
       "default_targets": [
         "All"
       ]
     }, 
     "gyp_env": {
       "GYP_CROSSCOMPILE": "1", 
-      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=['orderfiles', 'orderfile.out'] target_arch=ia32", 
+      "GYP_DEFINES": "OS=android chromium_win_pch=0 component=static_library fastbuild=1 gcc_version=46 host_os=linux order_text_section=Path([CHECKOUT], ('orderfiles', 'orderfile.out')) target_arch=ia32", 
       "GYP_GENERATORS": "ninja", 
       "GYP_GENERATOR_FLAGS": "default_target=All", 
       "GYP_MSVS_VERSION": "2010"
     }
   }, 
   "xcodebuild": "can not use xcodebuild on \"win\""
 }