Move FileCache, FileCacheMetadata and FileCacheObserver into internal namespace.

These are accessed only from classes under c/b/chromeos/drive/... so it's time
to move them into the internal namespace.

BUG=230235
TEST=Ran unit_tests
[email protected]

Review URL: https://codereview.chromium.org/14924005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@198626 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/chromeos/drive/file_cache.cc b/chrome/browser/chromeos/drive/file_cache.cc
index 8af47d3..6e312eb 100644
--- a/chrome/browser/chromeos/drive/file_cache.cc
+++ b/chrome/browser/chromeos/drive/file_cache.cc
@@ -22,6 +22,7 @@
 using content::BrowserThread;
 
 namespace drive {
+namespace internal {
 namespace {
 
 const base::FilePath::CharType kFileCacheMetaDir[] = FILE_PATH_LITERAL("meta");
@@ -1236,4 +1237,5 @@
   return cache_entry.is_persistent() ? CACHE_TYPE_PERSISTENT : CACHE_TYPE_TMP;
 }
 
+}  // namespace internal
 }  // namespace drive