Add support for GetHomeDir for Mac and Windows.

base/base_paths.h

Index: base/base_paths.h
diff --git a/base/base_paths.h b/base/base_paths.h
index f9601a290ae93d6a020553e6c12ad7f2bf94bbe3..26b2fd4c9a101e2cb8d1b5ca279495a6f40768bc 100644
--- a/base/base_paths.h
+++ b/base/base_paths.h
@@ -31,6 +31,10 @@ enum BasePathKey {
   DIR_EXE,           // Directory containing FILE_EXE.
   DIR_MODULE,        // Directory containing FILE_MODULE.
   DIR_TEMP,          // Temporary directory.
+  DIR_HOME,          // User's root home directory. On Windows this will look
+                     // like "C:\Users\you" (or on XP
+                     // "C:\Document and Settings\you") which isn't necessarily
+                     // a great place to put files.
   FILE_EXE,          // Path and filename of the current executable.
   FILE_MODULE,       // Path and filename of the module containing the code for
                      // the PathService (which could differ from FILE_EXE if the