Use a raw pointer instead of Singleton for PnaclHost and leak it.

components/nacl/browser/pnacl_host.h

Index: components/nacl/browser/pnacl_host.h
diff --git a/components/nacl/browser/pnacl_host.h b/components/nacl/browser/pnacl_host.h
index 268efeb0de2a5b71ae5440a1b780746cb1f1526a..ff3f04eba7da6a4ccab6193dfc2c4f89be0830c5 100644
--- a/components/nacl/browser/pnacl_host.h
+++ b/components/nacl/browser/pnacl_host.h
@@ -10,11 +10,9 @@
 #include <map>
 #include <memory>
 
-#include "base/callback_forward.h"
+#include "base/callback.h"
 #include "base/files/file.h"
 #include "base/macros.h"
-#include "base/memory/singleton.h"
-#include "base/memory/weak_ptr.h"
 #include "base/threading/thread_checker.h"
 #include "components/nacl/browser/nacl_file_host.h"
 #include "components/nacl/common/pnacl_types.h"
@@ -38,10 +36,17 @@ class PnaclHost {
   typedef base::Callback<void(base::File)> TempFileCallback;
   typedef base::Callback<void(const base::File&, bool is_hit)> NexeFdCallback;
 
+  // Gets the PnaclHost singleton instance (creating it if necessary).
+  // PnaclHost is a singleton because there is only one translation cache, and
+  // so that the BrowsingDataRemover can clear it even if no translation has
+  // ever been started.
   static PnaclHost* GetInstance();
 
-  PnaclHost();
-  ~PnaclHost();
+  // The PnaclHost instance is intentionally leaked on shutdown. DeInitIfSafe()
+  // attempts to cleanup |disk_cache_| earlier, but if it fails to do so in
+  // time, it will be too late when AtExitManager kicks in anway so subscribing
+  // to it is useless.
+  ~PnaclHost() = delete;
 
   // Initialize cache backend. GetNexeFd will also initialize the backend if
   // necessary, but calling Init ahead of time will minimize the latency.
@@ -99,16 +104,15 @@ class PnaclHost {
                                            const base::Closure& callback);
 
   // Return the number of tracked translations or FD requests currently pending.
-  size_t pending_translations() { return pending_translations_.size(); }
+  size_t pending_translations() {
+    DCHECK(thread_checker_.CalledOnValidThread());
+    return pending_translations_.size();
+  }
 
  private:
-  // PnaclHost is a singleton because there is only one translation cache, and
-  // so that the BrowsingDataRemover can clear it even if no translation has
-  // ever been started.
-  friend struct base::DefaultSingletonTraits<PnaclHost>;
   friend class FileProxy;
-  friend class pnacl::PnaclHostTest;
-  friend class pnacl::PnaclHostTestDisk;
+  friend class PnaclHostTest;
+  friend class PnaclHostTestDisk;
   enum CacheState {
     CacheUninitialized,
     CacheInitializing,
@@ -134,6 +138,9 @@ class PnaclHost {
 
   typedef std::pair<int, int> TranslationID;
   typedef std::map<TranslationID, PendingTranslation> PendingTranslationMap;
+
+  PnaclHost();
+
   static bool TranslationMayBeCached(
       const PendingTranslationMap::iterator& entry);
 
@@ -172,13 +179,12 @@ class PnaclHost {
 
   // Operations which are pending with the cache backend, which we should
   // wait for before destroying it (see comment on DeInitIfSafe).
-  int pending_backend_operations_;
-  CacheState cache_state_;
+  int pending_backend_operations_ = 0;
+  CacheState cache_state_ = CacheUninitialized;
   base::FilePath temp_dir_;
-  std::unique_ptr<pnacl::PnaclTranslationCache> disk_cache_;
+  std::unique_ptr<PnaclTranslationCache> disk_cache_;
   PendingTranslationMap pending_translations_;
   base::ThreadChecker thread_checker_;
-  base::WeakPtrFactory<PnaclHost> weak_factory_;
   DISALLOW_COPY_AND_ASSIGN(PnaclHost);
 };