Allows scons build to use local copy of platformsdk if one is not bundled sid...

build/SConscript.main

Index: build/SConscript.main
===================================================================
--- build/SConscript.main	(revision 6299)
+++ build/SConscript.main	(working copy)
@@ -249,11 +249,17 @@
 # as our source checkout.
 visual_studio_path = msvs_drive + ':/Program Files/Microsoft Visual Studio 8'
 
+# If side-by-side platform sdk is not available try local copy.
+platform_sdk_path = '$CHROME_SRC_DIR/third_party/platformsdk_vista_6_0/files'
+if (root_env['PLATFORM'] in ['win32', 'cygwin'] and
+    not os.path.exists(windows_env.subst(platform_sdk_path))):
+  platform_sdk_path = (
+      msvs_drive + ':\\Program Files\\Microsoft SDKs\\Windows\\v6.0')
+
 windows_env.Replace(
     CSCRIPT = 'c:\\Windows\\System32\\cscript',
 
-    PLATFORMSDK_VISTA_REL = '../third_party/platformsdk_vista_6_0',
-    PLATFORMSDK_VISTA = '$CHROME_SRC_DIR/third_party/platformsdk_vista_6_0',
+    PLATFORMSDK_VISTA = platform_sdk_path,
     VISUAL_STUDIO = visual_studio_path,
 
     CYGWIN_DIR = windows_env.Dir('$CHROME_SRC_DIR/third_party/cygwin'),