Fix PluginVmFilesTest to properly clear LSB-Release

The PluginVmFilesTest currently uses SetChromeOSVersionInfoForTest, but
this affects global state which is currently causing subsequent runs
of the unrelated PluginVmManager tests to fail. This CL changes this to
use the ScopedSetRunningOnChromeOSForTesting object instead.

Bug: 957477
Change-Id: Ie639e796aef536cd28bb884a310252b267b15270
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1611072Reviewed-by: Joel Hockey <joelhockey@chromium.org>
Commit-Queue: Timothy Loh <timloh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#659421}

chrome/browser/chromeos/plugin_vm/plugin_vm_files_unittest.cc

@@ -9,9 +9,9 @@
 #include "base/bind.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
-#include "base/system/sys_info.h"
 #include "base/time/time.h"
 #include "chrome/browser/chromeos/file_manager/path_util.h"
+#include "chrome/browser/chromeos/scoped_set_running_on_chromeos_for_testing.h"
 #include "chrome/test/base/testing_profile.h"
 #include "content/public/test/test_browser_thread_bundle.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ -28,14 +28,20 @@ class PluginVmFilesTest : public testing::Test {
 
   void SetUp() override {
     profile_ = std::make_unique<TestingProfile>();
-    base::SysInfo::SetChromeOSVersionInfoForTest(kLsbRelease, base::Time());
+    fake_release_ =
+        std::make_unique<chromeos::ScopedSetRunningOnChromeOSForTesting>(
+            kLsbRelease, base::Time());
   }
 
-  void TearDown() override { profile_.reset(); }
+  void TearDown() override {
+    fake_release_.reset();
+    profile_.reset();
+  }
 
  protected:
   content::TestBrowserThreadBundle thread_bundle_;
   std::unique_ptr<TestingProfile> profile_;
+  std::unique_ptr<chromeos::ScopedSetRunningOnChromeOSForTesting> fake_release_;
 };
 
 TEST_F(PluginVmFilesTest, DirNotExists) {