Chrome OS settings: Don't process avatar images on the UI thread

When the user selects a JPG file from disk to use as their profile image
we send the image to the renderer as a base64 encoded PNG. The PNG
encoding can be slow, so post a task to move encoding off the UI thread.

Test: Open OS settings > Personalization > Change device account image,
  and select a large JPEG. Select file window closing animation plays
  smoothly.

Bug: 812180
Change-Id: Ied7cebe1e85be580b5cd49e5ffb077815e73ebba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1826002
Commit-Queue: James Cook <jamescook@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Auto-Submit: James Cook <jamescook@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#700451}

chrome/browser/ui/webui/settings/chromeos/change_picture_handler.cc

@@ -17,6 +17,7 @@
 #include "base/stl_util.h"
 #include "base/strings/string_util.h"
 #include "base/strings/utf_string_conversions.h"
+#include "base/task/post_task.h"
 #include "base/values.h"
 #include "chrome/browser/chrome_notification_types.h"
 #include "chrome/browser/chromeos/accessibility/accessibility_manager.h"
@@ -225,11 +226,17 @@ void ChangePictureHandler::SendSelectedImage() {
           user->has_image_bytes()) {
         previous_image_bytes_ = user->image_bytes();
         SendOldImage(webui::GetPngDataUrl(previous_image_bytes_->front(),
-                                          previous_image_bytes_->size()),
-                     -1);
+                                          previous_image_bytes_->size()));
       } else {
         previous_image_bytes_ = nullptr;
-        SendOldImage(webui::GetBitmapDataUrl(*previous_image_.bitmap()), -1);
+        DCHECK(previous_image_.IsThreadSafe());
+        // Post a task because GetBitmapDataUrl does PNG encoding, which is
+        // slow for large images.
+        base::PostTaskAndReplyWithResult(
+            FROM_HERE, {base::ThreadPool(), base::TaskPriority::USER_BLOCKING},
+            base::BindOnce(&webui::GetBitmapDataUrl, *previous_image_.bitmap()),
+            base::BindOnce(&ChangePictureHandler::SendOldImage,
+                           weak_ptr_factory_.GetWeakPtr()));
       }
       break;
     }
@@ -250,7 +257,7 @@ void ChangePictureHandler::SendSelectedImage() {
         previous_image_ = user->GetImage();
         previous_image_bytes_ = nullptr;
         previous_image_format_ = user_manager::UserImage::FORMAT_UNKNOWN;
-        SendOldImage(
+        SendOldImageWithIndex(
             default_user_image::GetDefaultImageUrl(previous_image_index_),
             previous_image_index_);
       }
@@ -277,11 +284,15 @@ void ChangePictureHandler::UpdateProfileImage() {
   user_image_manager->DownloadProfileImage(kProfileDownloadReason);
 }
 
-void ChangePictureHandler::SendOldImage(const std::string& image_url,
+void ChangePictureHandler::SendOldImage(std::string&& image_url) {
+  SendOldImageWithIndex(std::move(image_url), -1);
+}
+
+void ChangePictureHandler::SendOldImageWithIndex(std::string&& image_url,
                                                  int image_index) {
   base::DictionaryValue result;
-  result.SetString("url", image_url);
-  result.SetInteger("index", image_index);
+  result.SetStringPath("url", std::move(image_url));
+  result.SetIntPath("index", image_index);
   FireWebUIListener("old-image-changed", result);
 }
 

chrome/browser/ui/webui/settings/chromeos/change_picture_handler.h

@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_UI_WEBUI_SETTINGS_CHROMEOS_CHANGE_PICTURE_HANDLER_H_
 
 #include "base/macros.h"
+#include "base/memory/weak_ptr.h"
 #include "base/scoped_observer.h"
 #include "chrome/browser/chromeos/camera_presence_notifier.h"
 #include "chrome/browser/image_decoder.h"
@@ -60,11 +61,14 @@ class ChangePictureHandler : public ::settings::SettingsPageUIHandler,
   // if any, on the page. Shouldn't be called before |SendProfileImage|.
   void UpdateProfileImage();
 
+  // Sends the previous user image to the page.
+  void SendOldImage(std::string&& image_url);
+
   // Sends the previous user image to the page. Also sends |image_index| which
   // is either the index of the previous user image (if it was from an older
   // default image set) or -1 otherwise. This allows the WebUI to show credits
   // for older default images.
-  void SendOldImage(const std::string& image_url, int image_index);
+  void SendOldImageWithIndex(std::string&& image_url, int image_index);
 
   // Starts camera presence check.
   void CheckCameraPresence();
@@ -139,6 +143,8 @@ class ChangePictureHandler : public ::settings::SettingsPageUIHandler,
       user_manager_observer_;
   ScopedObserver<CameraPresenceNotifier, ChangePictureHandler> camera_observer_;
 
+  base::WeakPtrFactory<ChangePictureHandler> weak_ptr_factory_{this};
+
   DISALLOW_COPY_AND_ASSIGN(ChangePictureHandler);
 };
 

ui/base/webui/web_ui_util.cc

@@ -36,8 +36,8 @@
 namespace webui {
 
 std::string GetBitmapDataUrl(const SkBitmap& bitmap) {
-  TRACE_EVENT2("oobe", "GetImageDataUrl",
-               "width", bitmap.width(), "height", bitmap.height());
+  TRACE_EVENT2("ui", "GetBitmapDataUrl", "width", bitmap.width(), "height",
+               bitmap.height());
   std::vector<unsigned char> output;
   gfx::PNGCodec::EncodeBGRASkBitmap(bitmap, false, &output);
   return GetPngDataUrl(output.data(), output.size());