Fix login visual hitch on chromebook

chrome/browser/image_decoder.h

Index: chrome/browser/image_decoder.h
diff --git a/chrome/browser/image_decoder.h b/chrome/browser/image_decoder.h
index 24f4d89bad6070486eb3b985f6a22b52143744f3..b1c9f19598dc8998f47f6f135667c341d073cc61 100644
--- a/chrome/browser/image_decoder.h
+++ b/chrome/browser/image_decoder.h
@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "base/compiler_specific.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/utility_process_host_client.h"
 
@@ -42,9 +43,13 @@ class ImageDecoder : public content::UtilityProcessHostClient {
                const std::string& image_data,
                ImageCodec image_codec);
 
-  // Starts image decoding.
+  // Starts image decoding on well-known threads.
   void Start();
 
+  // Starts image decoding on a sequence worker thread with a sequence token
+  // |sequence_token|.
+  void Start(const base::SequencedWorkerPool::SequenceToken& sequence_token);
+
   const std::vector<unsigned char>& get_image_data() const {
     return image_data_;
   }
@@ -58,6 +63,10 @@ class ImageDecoder : public content::UtilityProcessHostClient {
   // Overidden from UtilityProcessHostClient:
   virtual bool OnMessageReceived(const IPC::Message& message) OVERRIDE;
 
+  // True if on valid thread or named worker thread associated with
+  // |sequence_token_name_|.
+  bool CalledOnValidThreadOrWorkerThread();
+
   // IPC message handlers.
   void OnDecodeImageSucceeded(const SkBitmap& decoded_image);
   void OnDecodeImageFailed();
@@ -69,6 +78,8 @@ class ImageDecoder : public content::UtilityProcessHostClient {
   std::vector<unsigned char> image_data_;
   const ImageCodec image_codec_;
   content::BrowserThread::ID target_thread_id_;
+  base::SequencedWorkerPool::SequenceToken sequence_token_;
+  bool decode_on_sequence_worker_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(ImageDecoder);
 };