Eliminate CHECK from CryptohomeLibrary::LoadSystemSalt

chrome/browser/renderer_host/pepper/device_id_fetcher.h

Index: chrome/browser/renderer_host/pepper/device_id_fetcher.h
diff --git a/chrome/browser/renderer_host/pepper/device_id_fetcher.h b/chrome/browser/renderer_host/pepper/device_id_fetcher.h
index 1373bdffb236f4ee7e8499500f3a37c0c54b78e8..3a8c80e64edfb577c57dd1a89afc10e6791f9a82 100644
--- a/chrome/browser/renderer_host/pepper/device_id_fetcher.h
+++ b/chrome/browser/renderer_host/pepper/device_id_fetcher.h
@@ -12,6 +12,7 @@
 #include "base/compiler_specific.h"
 #include "base/files/file_path.h"
 #include "base/memory/ref_counted.h"
+#include "base/memory/weak_ptr.h"
 #include "ppapi/c/pp_instance.h"
 
 class Profile;
@@ -50,23 +51,24 @@ class DeviceIDFetcher : public base::RefCountedThreadSafe<DeviceIDFetcher> {
   ~DeviceIDFetcher();
 
   // Checks the preferences for DRM (whether DRM is enabled and getting the drm
-  // salt) on the UI thread. These are passed to |ComputeOnIOThread|.
+  // salt) on the UI thread.
   void CheckPrefsOnUIThread();
 
-  // Compute the device ID on the IO thread with the given salt.
-  void ComputeOnIOThread(const std::string& salt);
+  // Compute the device ID on the UI thread with the given salt and machine ID.
+  void ComputeOnUIThread(const std::string& salt,
+                         const std::string& machine_id);
+
   // Legacy method used to get the device ID for ChromeOS.
-  void ComputeOnBlockingPool(const base::FilePath& profile_path,
-                             const std::string& salt);
+  // static to avoid WeakPtr access on the blocking pool thread.
+  static void LegacyComputeOnBlockingPool(
+      base::WeakPtr<DeviceIDFetcher> fetcher,
+      const base::FilePath& profile_path,
+      const std::string& salt);
 
   // Runs the callback passed into Start() on the IO thread with the device ID
   // or the empty string on failure.
   void RunCallbackOnIOThread(const std::string& id);
 
-  // Helper which returns an ID unique to the system. Returns an empty string if
-  // the call fails.
-  std::string GetMachineID();
-
   friend class base::RefCountedThreadSafe<DeviceIDFetcher>;
 
   // The callback to run when the ID has been fetched.
@@ -77,6 +79,8 @@ class DeviceIDFetcher : public base::RefCountedThreadSafe<DeviceIDFetcher> {
 
   int render_process_id_;
 
+  base::WeakPtrFactory<DeviceIDFetcher> weak_ptr_factory_;
+
   DISALLOW_COPY_AND_ASSIGN(DeviceIDFetcher);
 };