Support WebP images in the IOSImageDecoderImpl

ios/chrome/browser/ntp_snippets/ios_chrome_content_suggestions_service_factory.cc

Index: ios/chrome/browser/ntp_snippets/ios_chrome_content_suggestions_service_factory.cc
diff --git a/ios/chrome/browser/ntp_snippets/ios_chrome_content_suggestions_service_factory.cc b/ios/chrome/browser/ntp_snippets/ios_chrome_content_suggestions_service_factory.cc
index 27969f5f93f2af28482abe89320c403d606d467a..db07a948d0a911efe3fec4ecaaa28e989b5a35bf 100644
--- a/ios/chrome/browser/ntp_snippets/ios_chrome_content_suggestions_service_factory.cc
+++ b/ios/chrome/browser/ntp_snippets/ios_chrome_content_suggestions_service_factory.cc
@@ -9,6 +9,7 @@
 #include "base/json/json_reader.h"
 #include "base/memory/ptr_util.h"
 #include "base/memory/singleton.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "base/values.h"
 #include "components/bookmarks/browser/bookmark_model.h"
@@ -52,7 +53,7 @@ using ntp_snippets::NTPSnippetsScheduler;
 using ntp_snippets::NTPSnippetsService;
 using ntp_snippets::NTPSnippetsStatusService;
 using suggestions::ImageFetcherImpl;
-using suggestions::IOSImageDecoderImpl;
+using suggestions::createIOSImageDecoder;
 using suggestions::SuggestionsService;
 using suggestions::SuggestionsServiceFactory;
 
@@ -155,6 +156,9 @@ IOSChromeContentSuggestionsServiceFactory::BuildServiceInstanceFor(
             ->GetSequencedTaskRunnerWithShutdownBehavior(
                 base::SequencedWorkerPool::GetSequenceToken(),
                 base::SequencedWorkerPool::CONTINUE_ON_SHUTDOWN);
+    scoped_refptr<base::SequencedWorkerPool> image_decoder_worker_pool(

[sdefresne, 2016/10/05 09:15:28]

Creation of base::SequencePool directly is really uncommon in Chromium code
(there's only a few occurrence outside of tests
https://cs.chromium.org/search/?q=new%5C+base::SequencedWorkerPool+-file:.*te...).

Instead, the recommended way is to use the blocking pool from WebThread (for
ios) or BrowserThread (for the other platforms), just like is done a few lines
above. So I would remove this local variable and instead pass "task_runner" to
"createIOSImageDecoder". If you want the tasks to be independent, then ask the
blocking pool for another task runner (by adding another invocation of
web::WebThread::GetBlockingPool()->GetSequencedTaskRunnerWithShutdownBehavior(...)).

[vitaliii, 2016/10/06 06:35:08]

Done, thanks for detailed explanation!

+        new base::SequencedWorkerPool(/*max_threads*/ 2, "ImageDecoding",
+                                      base::TaskPriority::USER_VISIBLE));
     std::unique_ptr<NTPSnippetsService> ntp_snippets_service =
         base::MakeUnique<NTPSnippetsService>(
             service.get(), service->category_factory(), prefs,
@@ -168,7 +172,7 @@ IOSChromeContentSuggestionsServiceFactory::BuildServiceInstanceFor(
                     : google_apis::GetNonStableAPIKey()),
             base::MakeUnique<ImageFetcherImpl>(
                 request_context.get(), web::WebThread::GetBlockingPool()),
-            base::MakeUnique<IOSImageDecoderImpl>(),
+            createIOSImageDecoder(image_decoder_worker_pool),
             base::MakeUnique<NTPSnippetsDatabase>(database_dir, task_runner),
             base::MakeUnique<NTPSnippetsStatusService>(signin_manager, prefs));
     service->set_ntp_snippets_service(ntp_snippets_service.get());