Reland of reduce dependencies on rtc::FileSystem in FileRotatingStream tests... (patchset #1 id:1 of https://codereview.webrtc.org/2885393002/ )

Reason for revert:
Downstream project now fixed.

Original issue's description:
> Revert of Reduce dependencies on rtc::FileSystem in FileRotatingStream tests, adding helpers in webrtc::test:: (patchset #7 id:120001 of https://codereview.webrtc.org/2872283002/ )
>
> Reason for revert:
> Fails to compile successfully.
>
>
> Original issue's description:
> > Reduce dependencies on rtc::FileSystem in FileRotatingStream tests.
> >
> > Use webrtc::test::OutputPath instead of Filesystem::GetAppTempFolder.
> > Added functions RemoveFile and RemoveDir in the webrtc::test namespace,
> > to replace use of Filesystem::DeleteFolderAndContents.
> >
> > This makes Filesystem::DeleteFolderAndContents unused, to be deleted
> > together with related code in a followup cl.
> >
> > BUG=webrtc:7345
> >
> > Review-Url: https://codereview.webrtc.org/2872283002
> > Cr-Commit-Position: refs/heads/master@{#18173}
> > Committed: https://chromium.googlesource.com/external/webrtc/+/dd7b5f32b59d9def668b9e9487589a572f20f6e0
>
> TBR=pthatcher@webrtc.org,kjellander@webrtc.org,tommi@webrtc.org,nisse@webrtc.org
> # Skipping CQ checks because original CL landed less than 1 days ago.
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
> BUG=webrtc:7345
>
> Review-Url: https://codereview.webrtc.org/2885393002
> Cr-Commit-Position: refs/heads/master@{#18180}
> Committed: https://chromium.googlesource.com/external/webrtc/+/deaa33d2f59783e849ddc01428be807d92431983

TBR=pthatcher@webrtc.org,kjellander@webrtc.org,tommi@webrtc.org,ehmaldonado@webrtc.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:7345

Review-Url: https://codereview.webrtc.org/2885413002
Cr-Commit-Position: refs/heads/master@{#18193}
diff --git a/webrtc/base/filerotatingstream_unittest.cc b/webrtc/base/filerotatingstream_unittest.cc
index 2a0e858..7acb174 100644
--- a/webrtc/base/filerotatingstream_unittest.cc
+++ b/webrtc/base/filerotatingstream_unittest.cc
@@ -16,9 +16,21 @@
 #include "webrtc/base/fileutils.h"
 #include "webrtc/base/gunit.h"
 #include "webrtc/base/pathutils.h"
+#include "webrtc/test/testsupport/fileutils.h"
 
 namespace rtc {
 
+namespace {
+
+void CleanupLogDirectory(const FileRotatingStream& stream) {
+  for (size_t i = 0; i < stream.GetNumFiles(); ++i) {
+    // Ignore return value, not all files are expected to exist.
+    webrtc::test::RemoveFile(stream.GetFilePath(i));
+  }
+}
+
+}  // namespace
+
 #if defined (WEBRTC_ANDROID)
 // Fails on Android: https://bugs.chromium.org/p/webrtc/issues/detail?id=4364.
 #define MAYBE_FileRotatingStreamTest DISABLED_FileRotatingStreamTest
@@ -35,23 +47,23 @@
             const std::string& file_prefix,
             size_t max_file_size,
             size_t num_log_files) {
-    Pathname test_path;
-    ASSERT_TRUE(Filesystem::GetAppTempFolder(&test_path));
+    dir_path_ = webrtc::test::OutputPath();
+
     // Append per-test output path in order to run within gtest parallel.
-    test_path.AppendFolder(dir_name);
-    ASSERT_TRUE(Filesystem::CreateFolder(test_path));
-    dir_path_ = test_path.pathname();
-    ASSERT_TRUE(dir_path_.size());
+    dir_path_.append(dir_name);
+    dir_path_.push_back(Pathname::DefaultFolderDelimiter());
+    ASSERT_TRUE(webrtc::test::CreateDir(dir_path_));
     stream_.reset(new FileRotatingStream(dir_path_, file_prefix, max_file_size,
                                          num_log_files));
   }
 
   void TearDown() override {
+    // On windows, open files can't be removed.
+    stream_->Close();
+    CleanupLogDirectory(*stream_);
+    EXPECT_TRUE(webrtc::test::RemoveDir(dir_path_));
+
     stream_.reset();
-    if (dir_path_.size() && Filesystem::IsFolder(dir_path_) &&
-        Filesystem::IsTemporaryPath(dir_path_)) {
-      Filesystem::DeleteFolderAndContents(dir_path_);
-    }
   }
 
   // Writes the data to the stream and flushes it.
@@ -204,23 +216,23 @@
 class MAYBE_CallSessionFileRotatingStreamTest : public ::testing::Test {
  protected:
   void Init(const std::string& dir_name, size_t max_total_log_size) {
-    Pathname test_path;
-    ASSERT_TRUE(Filesystem::GetAppTempFolder(&test_path));
+    dir_path_ = webrtc::test::OutputPath();
+
     // Append per-test output path in order to run within gtest parallel.
-    test_path.AppendFolder(dir_name);
-    ASSERT_TRUE(Filesystem::CreateFolder(test_path));
-    dir_path_ = test_path.pathname();
-    ASSERT_TRUE(dir_path_.size());
+    dir_path_.append(dir_name);
+    dir_path_.push_back(Pathname::DefaultFolderDelimiter());
+    ASSERT_TRUE(webrtc::test::CreateDir(dir_path_));
     stream_.reset(
         new CallSessionFileRotatingStream(dir_path_, max_total_log_size));
   }
 
   virtual void TearDown() {
+    // On windows, open files can't be removed.
+    stream_->Close();
+    CleanupLogDirectory(*stream_);
+    EXPECT_TRUE(webrtc::test::RemoveDir(dir_path_));
+
     stream_.reset();
-    if (dir_path_.size() && Filesystem::IsFolder(dir_path_) &&
-        Filesystem::IsTemporaryPath(dir_path_)) {
-      Filesystem::DeleteFolderAndContents(dir_path_);
-    }
   }
 
   // Writes the data to the stream and flushes it.