Re-land: base: Implement browser process support for discardable memory.

ash/test/test_suite.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ash/test/test_suite.h"
 
 #include "ash/ash_switches.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "build/build_config.h"
@@ skipping 34 matching lines @@
   }
 #endif
 
   gfx::RegisterPathProvider();
   ui::RegisterPathProvider();
 
   // Force unittests to run using en-US so if we test against string
   // output, it'll pass regardless of the system language.
   ui::ResourceBundle::InitSharedInstanceWithLocale(
       "en-US", NULL, ui::ResourceBundle::LOAD_COMMON_RESOURCES);
+
+  base::DiscardableMemoryShmemAllocator::SetInstance(
+      &discardable_memory_allocator_);
 }
 
 void AuraShellTestSuite::Shutdown() {
   ui::ResourceBundle::CleanupSharedInstance();
 #if defined(OS_WIN)
   com_initializer_.reset();
 #endif
   base::TestSuite::Shutdown();
 }
 
 }  // namespace test
 }  // namespace ash