[Memory] Move OomPriorityManager out of chromeos specific files.

This adds the concept of oom manager to all platforms, but stays disabled on all except CrOS.

Note: This is CL #3 towards expanding Chromeos tab killing to other platforms.

BUG=463597

Review URL: https://codereview.chromium.org/1213783003

Cr-Commit-Position: refs/heads/master@{#336770}
diff --git a/chrome/browser/browser_process_impl.cc b/chrome/browser/browser_process_impl.cc
index 2b060c1..330ff8a 100644
--- a/chrome/browser/browser_process_impl.cc
+++ b/chrome/browser/browser_process_impl.cc
@@ -147,6 +147,10 @@
 #include "chrome/browser/media/webrtc_log_uploader.h"
 #endif
 
+#if defined(OS_CHROMEOS)
+#include "chrome/browser/memory/oom_priority_manager.h"
+#endif
+
 #if (defined(OS_WIN) || defined(OS_LINUX)) && !defined(OS_CHROMEOS)
 // How often to check if the persistent instance of Chrome needs to restart
 // to install an update.
@@ -767,6 +771,17 @@
   return gcm_driver_.get();
 }
 
+memory::OomPriorityManager* BrowserProcessImpl::GetOomPriorityManager() {
+  DCHECK(CalledOnValidThread());
+#if defined(OS_CHROMEOS)
+  if (!oom_priority_manager_.get())
+    oom_priority_manager_.reset(new memory::OomPriorityManager());
+  return oom_priority_manager_.get();
+#else
+  return nullptr;
+#endif
+}
+
 // static
 void BrowserProcessImpl::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterBooleanPref(prefs::kDefaultBrowserSettingEnabled,