Make FileManagerDialog::SelectFileImpl() properly accept simple filenames as default path.

This affects Chrome OS.

1 - If the default path provided isn't managed by the external filesystem
    provider, still keep the base (i.e., file) name.
2 - Fix the JS regex so that it splits the directory/leaf names correctly when
    no path is provided.

BUG=http://code.google.com/p/chromium-os/issues/detail?id=22184
TEST=The main test is that sufficiently-recent Pepper Flash should provide
     correct (Flash) Save As functionality, including the default filename;
     e.g., http://www.everythingflex.com/flex3_fp10/savetodisk/SaveToDisk.html .
     Also, "Save As" for HTML should also provide a default filename on Linux
     chromeos=1 builds.


Review URL: http://codereview.chromium.org/8414006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@108009 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/resources/file_manager/js/file_manager.js

@@ -1274,7 +1274,7 @@ FileManager.prototype = {
 
   FileManager.prototype.setupPath_ = function(path) {
     // Split the dirname from the basename.
-    var ary = path.match(/^(.*?)(?:\/([^\/]+))?$/);
+    var ary = path.match(/^(?:(.*)\/)?([^\/]*)$/);
     if (!ary) {
       console.warn('Unable to split default path: ' + path);
       self.changeDirectory('/', CD_NO_HISTORY);

chrome/browser/ui/views/file_manager_dialog.cc

@@ -199,7 +199,7 @@ void FileManagerDialog::SelectFileImpl(
   FilePath virtual_path;
   if (!FileManagerUtil::ConvertFileToRelativeFileSystemPath(
           owner_browser->profile(), default_path, &virtual_path)) {
-    virtual_path = FilePath();
+    virtual_path = default_path.BaseName();
   }
 
   hasMultipleFileTypeChoices_ =