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

components/favicon/core/large_icon_service.cc

Index: components/favicon/core/large_icon_service.cc
diff --git a/components/favicon/core/large_icon_service.cc b/components/favicon/core/large_icon_service.cc
index ed1a17f46375f1da5d11f6e74f0ae9962585070e..a244b0ec57a941338e83403eb39fb6d46daacc69 100644
--- a/components/favicon/core/large_icon_service.cc
+++ b/components/favicon/core/large_icon_service.cc
@@ -4,110 +4,203 @@
 
 #include "components/favicon/core/large_icon_service.h"
 
+#include "base/bind.h"
+#include "base/logging.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.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 favicon {
-
-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);
+namespace {
+
+// Processes the bitmap data returned from the FaviconService as part of a
+// LargeIconService request.
+class LargeIconWorker : public base::RefCountedThreadSafe<LargeIconWorker> {
+ public:
+  LargeIconWorker(int min_source_size_in_pixel,
+                  int desired_size_in_pixel,
+                  favicon_base::LargeIconCallback callback,
+                  scoped_refptr<base::TaskRunner> background_task_runner,
+                  base::CancelableTaskTracker* tracker);
+
+  // Must run on the owner (UI) thread in production.
+  // Intermediate callback for GetLargeIconOrFallbackStyle(). Invokes
+  // ProcessIconOnBackgroundThread() so we do not perform complex image
+  // operations on the UI thread.
+  void OnIconLookupComplete(
+      const favicon_base::FaviconRawBitmapResult& bitmap_result);
+
+ private:
+  friend class base::RefCountedThreadSafe<LargeIconWorker>;
+
+  ~LargeIconWorker();
+
+  // Must run on a background thread in production.
+  // Tries to resize |bitmap_result_| and pass the output to |callback_|. If
+  // that does not work, computes the icon fallback style and uses it to
+  // invoke |callback_|. This must be run on a background thread because image
+  // resizing and dominant color extraction can be expensive.
+  void ProcessIconOnBackgroundThread();
+
+  // Must run on a background thread in production.
+  // If |bitmap_result_| is square and large enough (>= |min_source_in_pixel_|),
+  // resizes it to |desired_size_in_pixel_| (but if |desired_size_in_pixel_| is
+  // 0 then don't resize). If successful, stores the resulting bitmap data
+  // into |resized_bitmap_result| and returns true.
+  bool ResizeLargeIconOnBackgroundThreadIfValid(
+      favicon_base::FaviconRawBitmapResult* resized_bitmap_result);
+
+  // Must run on the owner (UI) thread in production.
+  // Invoked when ProcessIconOnBackgroundThread() is done.
+  void OnIconProcessingComplete();
+
+  int min_source_size_in_pixel_;
+  int desired_size_in_pixel_;
+  favicon_base::LargeIconCallback callback_;
+  scoped_refptr<base::TaskRunner> background_task_runner_;
+  base::CancelableTaskTracker* tracker_;
+  favicon_base::FaviconRawBitmapResult bitmap_result_;
+  scoped_ptr<favicon_base::LargeIconResult> result_;
+
+  DISALLOW_COPY_AND_ASSIGN(LargeIconWorker);
+};
+
+LargeIconWorker::LargeIconWorker(
+    int min_source_size_in_pixel,
+    int desired_size_in_pixel,
+    favicon_base::LargeIconCallback callback,
+    scoped_refptr<base::TaskRunner> background_task_runner,
+    base::CancelableTaskTracker* tracker)
+    : min_source_size_in_pixel_(min_source_size_in_pixel),
+      desired_size_in_pixel_(desired_size_in_pixel),
+      callback_(callback),
+      background_task_runner_(background_task_runner),
+      tracker_(tracker) {
 }
 
-LargeIconService::~LargeIconService() {
+LargeIconWorker::~LargeIconWorker() {
 }
 
-base::CancelableTaskTracker::TaskId
-    LargeIconService::GetLargeIconOrFallbackStyle(
-        const GURL& page_url,
-        int min_source_size_in_pixel,
-        int desired_size_in_pixel,
-        const favicon_base::LargeIconCallback& callback,
-        base::CancelableTaskTracker* tracker) {
-  DCHECK_LE(1, min_source_size_in_pixel);
-  DCHECK_LE(0, desired_size_in_pixel);
+void LargeIconWorker::OnIconLookupComplete(
+    const favicon_base::FaviconRawBitmapResult& bitmap_result) {
+  bitmap_result_ = bitmap_result;
+  tracker_->PostTaskAndReply(
+      background_task_runner_.get(), FROM_HERE,
+      base::Bind(&LargeIconWorker::ProcessIconOnBackgroundThread, this),
+      base::Bind(&LargeIconWorker::OnIconProcessingComplete, this));
+}
 
-  // 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_,
-      std::max(min_source_size_in_pixel, desired_size_in_pixel),
-      base::Bind(&LargeIconService::RunLargeIconCallback,
-                 base::Unretained(this), callback, min_source_size_in_pixel,
-                 desired_size_in_pixel),
-      tracker);
+void LargeIconWorker::ProcessIconOnBackgroundThread() {
+  favicon_base::FaviconRawBitmapResult resized_bitmap_result;
+  if (ResizeLargeIconOnBackgroundThreadIfValid(&resized_bitmap_result)) {
+    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 (bitmap_result_.is_valid()) {
+      favicon_base::SetDominantColorAsBackground(
+          bitmap_result_.bitmap_data, fallback_icon_style.get());
+    }
+    result_.reset(
+        new favicon_base::LargeIconResult(fallback_icon_style.release()));
+  }
 }
 
-bool LargeIconService::ResizeLargeIconIfValid(
-    int min_source_size_in_pixel,
-    int desired_size_in_pixel,
-    const favicon_base::FaviconRawBitmapResult& bitmap_result,
+bool LargeIconWorker::ResizeLargeIconOnBackgroundThreadIfValid(
     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())
+  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() < min_source_size_in_pixel)
+  if (bitmap_result_.pixel_size.width() < min_source_size_in_pixel_)
     return false;
 
-  *resized_bitmap_result = bitmap_result;
+  *resized_bitmap_result = bitmap_result_;
 
-  // Special case: Can use |bitmap_result| as is.
-  if (desired_size_in_pixel == 0 ||
-      bitmap_result.pixel_size.width() == desired_size_in_pixel)
+  // Special case: Can use |bitmap_result_| as is.
+  if (desired_size_in_pixel_ == 0 ||
+      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))
+  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);
+      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);
+      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 min_source_size_in_pixel,
-    int desired_size_in_pixel,
-    const favicon_base::FaviconRawBitmapResult& bitmap_result) {
-  favicon_base::FaviconRawBitmapResult resized_bitmap_result;
-  if (ResizeLargeIconIfValid(min_source_size_in_pixel, desired_size_in_pixel,
-                             bitmap_result, &resized_bitmap_result)) {
-    callback.Run(favicon_base::LargeIconResult(resized_bitmap_result));
-    return;
-  }
+void LargeIconWorker::OnIconProcessingComplete() {
+  callback_.Run(*result_);
+}
 
-  // 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);
+}  // namespace
+
+namespace favicon {
+
+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 min_source_size_in_pixel,
+        int desired_size_in_pixel,
+        const favicon_base::LargeIconCallback& callback,
+        base::CancelableTaskTracker* tracker) {
+  DCHECK_LE(1, min_source_size_in_pixel);
+  DCHECK_LE(0, desired_size_in_pixel);
+
+  scoped_refptr<LargeIconWorker> worker =
+      new LargeIconWorker(min_source_size_in_pixel,
+          desired_size_in_pixel, callback, GetBackgroundTaskRunner(), 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(&LargeIconWorker::OnIconLookupComplete, worker),
+      tracker);
+}
+
+// Returns TaskRunner used to execute background task.
+scoped_refptr<base::TaskRunner> LargeIconService::GetBackgroundTaskRunner() {
+  return content::BrowserThread::GetBlockingPool()
+      ->GetTaskRunnerWithShutdownBehavior(
+          base::SequencedWorkerPool::SKIP_ON_SHUTDOWN);
 }
 
 }  // namespace favicon