[Large Icon Service] Move icon resizing into worker thread.

components/favicon/core/large_icon_service.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/favicon/core/large_icon_service.h"
 
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/task_runner.h"
+#include "base/threading/sequenced_worker_pool.h"
 #include "components/favicon/core/favicon_service.h"
 #include "components/favicon_base/fallback_icon_style.h"
-#include "components/favicon_base/favicon_types.h"
+#include "content/public/browser/browser_thread.h"
 #include "skia/ext/image_operations.h"
 #include "ui/gfx/codec/png_codec.h"
 #include "ui/gfx/geometry/size.h"
 
+namespace {
+
+// Return a TaskRunner used to execute background task.

[pkotwicz, 2015/05/07 14:52:14]

Nit: "Return TaskRunner" (no "a")

[huangs, 2015/05/07 21:01:58]

Done, also using "Returns".

+scoped_refptr<base::TaskRunner> GetBackgroundTaskRunner() {
+  return content::BrowserThread::GetBlockingPool()
+      ->GetTaskRunnerWithShutdownBehavior(
+          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
+}
+
+}  // namespace
+
 namespace favicon {
 
+LargeIconService::Session::Session()
+    : desired_size_in_pixel(0),
+      tracker(nullptr) {
+}
+
+LargeIconService::Session::~Session() {
+}
+
 LargeIconService::LargeIconService(FaviconService* favicon_service)
     : favicon_service_(favicon_service) {
   large_icon_types_.push_back(favicon_base::IconType::FAVICON);
   large_icon_types_.push_back(favicon_base::IconType::TOUCH_ICON);
   large_icon_types_.push_back(favicon_base::IconType::TOUCH_PRECOMPOSED_ICON);
 }
 
 LargeIconService::~LargeIconService() {
 }
 
 base::CancelableTaskTracker::TaskId
     LargeIconService::GetLargeIconOrFallbackStyle(
         const GURL& page_url,
         int desired_size_in_pixel,
         const favicon_base::LargeIconCallback& callback,
         base::CancelableTaskTracker* tracker) {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  scoped_refptr<LargeIconService::Session> session =
+      new LargeIconService::Session();
+  session->desired_size_in_pixel = desired_size_in_pixel;
+  session->callback = callback;
+  session->tracker = tracker;
+
   // TODO(beaudoin): For now this is just a wrapper around
   //   GetLargestRawFaviconForPageURL. Add the logic required to select the best
   //   possible large icon. Also add logic to fetch-on-demand when the URL of
   //   a large icon is known but its bitmap is not available.
   return favicon_service_->GetLargestRawFaviconForPageURL(
-      page_url,
-      large_icon_types_,
-      desired_size_in_pixel,
-      base::Bind(&LargeIconService::RunLargeIconCallback,
-                 base::Unretained(this), callback, desired_size_in_pixel),
+      page_url, large_icon_types_, desired_size_in_pixel,
+      base::Bind(&LargeIconService::OnIconLookupComplete, session),
       tracker);
 }
 
+// static
 bool LargeIconService::ResizeLargeIconIfValid(

[pkotwicz, 2015/05/07 14:52:14]

Can you please add the "OnBackgroundThread" suffix to the method name for the
sake of consistency?

[huangs, 2015/05/07 21:01:58]

Done, but "IfValid" wins as suffix.

     int desired_size_in_pixel,
     const favicon_base::FaviconRawBitmapResult& bitmap_result,
     favicon_base::FaviconRawBitmapResult* resized_bitmap_result) {
   // Require bitmap to be valid and square.
   if (!bitmap_result.is_valid() ||
       bitmap_result.pixel_size.width() != bitmap_result.pixel_size.height())
     return false;
 
   // Require bitmap to be large enough. It's square, so just check width.
   if (bitmap_result.pixel_size.width() < desired_size_in_pixel) {
     // TODO(beaudoin): Potentially relax this, and allow icon to be scaled up.
     return false;
   }
 
   *resized_bitmap_result = bitmap_result;
-
   // Special case: Can use |resized_bitmap_result| as is.
   if (bitmap_result.pixel_size.width() == desired_size_in_pixel)
     return true;
 
   // Resize bitmap: decode PNG, resize, and re-encode PNG.
   SkBitmap decoded_bitmap;
   if (!gfx::PNGCodec::Decode(bitmap_result.bitmap_data->front(),
           bitmap_result.bitmap_data->size(), &decoded_bitmap))
     return false;
 
   SkBitmap resized_bitmap = skia::ImageOperations::Resize(
       decoded_bitmap, skia::ImageOperations::RESIZE_LANCZOS3,
       desired_size_in_pixel, desired_size_in_pixel);
 
   std::vector<unsigned char> bitmap_data;
   if (!gfx::PNGCodec::EncodeBGRASkBitmap(resized_bitmap, false, &bitmap_data))
     return false;
 
   resized_bitmap_result->pixel_size =
       gfx::Size(desired_size_in_pixel, desired_size_in_pixel);
   resized_bitmap_result->bitmap_data =
       base::RefCountedBytes::TakeVector(&bitmap_data);
   return true;
 }
 
-void LargeIconService::RunLargeIconCallback(
-    const favicon_base::LargeIconCallback& callback,
-    int desired_size_in_pixel,
+// static
+void LargeIconService::OnIconLookupComplete(
+    scoped_refptr<LargeIconService::Session> session,
     const favicon_base::FaviconRawBitmapResult& bitmap_result) {
+  session->bitmap_result = bitmap_result;
+  session->tracker->PostTask(
+      GetBackgroundTaskRunner().get(), FROM_HERE,
+      base::Bind(&LargeIconService::ProcessIconOnBackgroundThread, session));
+}
+
+// static
+void LargeIconService::ProcessIconOnBackgroundThread(
+    scoped_refptr<LargeIconService::Session> session) {
+  DCHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
   favicon_base::FaviconRawBitmapResult resized_bitmap_result;
-  if (ResizeLargeIconIfValid(desired_size_in_pixel, bitmap_result,
-                             &resized_bitmap_result)) {
-    callback.Run(favicon_base::LargeIconResult(resized_bitmap_result));
-    return;
+  if (ResizeLargeIconIfValid(session->desired_size_in_pixel,
+                             session->bitmap_result, &resized_bitmap_result)) {
+    session->result.reset(
+        new favicon_base::LargeIconResult(resized_bitmap_result));
+  } else {
+    // Failed to resize |bitmap_result|, so compute fallback icon style.
+    scoped_ptr<favicon_base::FallbackIconStyle> fallback_icon_style(
+        new favicon_base::FallbackIconStyle());
+    if (session->bitmap_result.is_valid()) {
+      favicon_base::SetDominantColorAsBackground(
+          session->bitmap_result.bitmap_data, fallback_icon_style.get());
+    }
+    session->result.reset(
+        new favicon_base::LargeIconResult(fallback_icon_style.release()));
   }
 
-  // Failed to resize |bitmap_result|, so compute fallback icon style.
-  favicon_base::LargeIconResult result(new favicon_base::FallbackIconStyle());
-  if (bitmap_result.is_valid()) {
-    favicon_base::SetDominantColorAsBackground(
-        bitmap_result.bitmap_data, result.fallback_icon_style.get());
-  }
-  callback.Run(result);
+  content::BrowserThread::PostTask(
+      content::BrowserThread::UI, FROM_HERE,
+      base::Bind(&LargeIconService::OnIconProcessingComplete, session));

[pkotwicz, 2015/05/07 14:52:14]

Is there a reason that you pass the session object to OnIconProcessingComplete()
instead of LargeIconResult?

[huangs, 2015/05/07 21:01:58]

Using session->callback and session->result.  And even if one is used I'd still
pass |session| for consistency.

Moot now due to recent update.

+}
+
+// static
+void LargeIconService::OnIconProcessingComplete(
+    scoped_refptr<LargeIconService::Session> session) {
+  DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  session->callback.Run(*session->result);
 }
 
 }  // namespace favicon