Remove unused dependencies from drive_test_util.h

Bug: 911287
Change-Id: I5a996d514ad082fa84551a75d0ab2abf4caba710
Reviewed-on: https://chromium-review.googlesource.com/c/1474845
Reviewed-by: Naoki Fukino <fukino@chromium.org>
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/master@{#632520}

components/drive/chromeos/drive_test_util.h

@@ -12,17 +12,11 @@
 #include "components/drive/chromeos/file_cache.h"
 #include "content/public/test/test_utils.h"
 #include "google_apis/drive/test_util.h"
-#include "net/base/completion_callback.h"
 #include "net/base/io_buffer.h"
-#include "net/base/network_change_notifier.h"
 #include "net/base/test_completion_callback.h"
 
 class PrefRegistrySimple;
 
-namespace net {
-class IOBuffer;
-}  // namespace net
-
 namespace drive {
 
 namespace test_util {