Move PathIsWritable, DirectoryExists, ContentsEqual, and TextContentsEqual to the base namespace.

chrome/browser/extensions/webstore_installer.cc

Index: chrome/browser/extensions/webstore_installer.cc
diff --git a/chrome/browser/extensions/webstore_installer.cc b/chrome/browser/extensions/webstore_installer.cc
index 2b14cf53d74492ea905013a8ba287c322ba1e3e2..44b6450c3955a0d5f2dc5964ca8da50999ff3466 100644
--- a/chrome/browser/extensions/webstore_installer.cc
+++ b/chrome/browser/extensions/webstore_installer.cc
@@ -88,7 +88,7 @@ void GetDownloadFilePath(
 
   // Ensure the download directory exists. TODO(asargent) - make this use
   // common code from the downloads system.
-  if (!file_util::DirectoryExists(directory)) {
+  if (!base::DirectoryExists(directory)) {
     if (!file_util::CreateDirectory(directory)) {
       BrowserThread::PostTask(BrowserThread::UI, FROM_HERE,
                               base::Bind(callback, base::FilePath()));