Add some error messages for setting wallpaper failures on Chrome(c++) side.

chrome/browser/chromeos/extensions/wallpaper_private_api.cc

 // Copyright (c) 2012 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 "chrome/browser/chromeos/extensions/wallpaper_private_api.h"
 
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/shell.h"
 #include "base/file_util.h"
 #include "base/json/json_writer.h"
@@ skipping 83 matching lines @@
 
   void Cancel() {
     cancel_flag_.Set();
   }
 
   virtual void OnImageDecoded(const ImageDecoder* decoder,
                               const SkBitmap& decoded_image) OVERRIDE {
     gfx::ImageSkia final_image(decoded_image);
     final_image.MakeThreadSafe();
     if (cancel_flag_.IsSet()) {
-      function_->OnFailureOrCancel();
+      function_->OnFailureOrCancel("");
       delete this;
       return;
     }
     function_->OnWallpaperDecoded(final_image);
     delete this;
   }
 
   virtual void OnDecodeImageFailed(const ImageDecoder* decoder) OVERRIDE {
-    function_->OnFailureOrCancel();
-    // TODO(bshe): Dispatches an encoding error event.
+    function_->OnFailureOrCancel(
+        l10n_util::GetStringUTF8(IDS_WALLPAPER_MANAGER_INVALID_WALLPAPER));
     delete this;
   }
 
  private:
   scoped_refptr<WallpaperFunctionBase> function_;
   scoped_refptr<ImageDecoder> image_decoder_;
   base::CancellationFlag cancel_flag_;
 
   DISALLOW_COPY_AND_ASSIGN(WallpaperDecoder);
 };
 
 WallpaperFunctionBase::WallpaperDecoder*
     WallpaperFunctionBase::wallpaper_decoder_;
 
 WallpaperFunctionBase::WallpaperFunctionBase() {
 }
 
 WallpaperFunctionBase::~WallpaperFunctionBase() {
 }
 
+void WallpaperFunctionBase::OnFailureOrCancel(const std::string& error) {
+  wallpaper_decoder_ = NULL;
+  if (!error.empty())
+    SetError(error);
+  SendResponse(false);
+}
+
 WallpaperSetWallpaperFunction::WallpaperSetWallpaperFunction() {
 }
 
 WallpaperSetWallpaperFunction::~WallpaperSetWallpaperFunction() {
 }
 
 bool WallpaperSetWallpaperFunction::RunImpl() {
   BinaryValue* input = NULL;
   if (args_ == NULL || !args_->GetBinary(0, &input)) {
     return false;
@@ skipping 22 matching lines @@
     const gfx::ImageSkia& wallpaper) {
   wallpaper_ = wallpaper;
   // Set wallpaper_decoder_ to null since the decoding already finished.
   wallpaper_decoder_ = NULL;
   BrowserThread::PostTask(
       BrowserThread::FILE, FROM_HERE,
       base::Bind(&WallpaperSetWallpaperFunction::SaveToFile,
                  this));
 }
 
-void WallpaperSetWallpaperFunction::OnFailureOrCancel() {
-  wallpaper_decoder_ = NULL;
-  SendResponse(false);
-}
-
 void WallpaperSetWallpaperFunction::SaveToFile() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
   FilePath wallpaper_dir;
   CHECK(PathService::Get(chrome::DIR_CHROMEOS_WALLPAPERS, &wallpaper_dir));
   if (!file_util::DirectoryExists(wallpaper_dir) &&
       !file_util::CreateDirectory(wallpaper_dir)) {
     BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE,
         base::Bind(&WallpaperSetWallpaperFunction::OnFailureOrCancel,
-                   this));
+                   this, ""));
+    LOG(ERROR) << "Failed to create wallpaper directory.";
     return;
   }
   std::string file_name = GURL(url_).ExtractFileName();
   FilePath file_path = wallpaper_dir.Append(file_name);
   if (file_util::PathExists(file_path) ||
       file_util::WriteFile(file_path, image_data_.c_str(),
                            image_data_.size()) != -1 ) {
     BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE,
         base::Bind(&WallpaperSetWallpaperFunction::SetDecodedWallpaper,
                    this));
     chromeos::UserImage wallpaper(wallpaper_);
 
     // Generates and saves small resolution wallpaper. Uses CENTER_CROPPED to
     // maintain the aspect ratio after resize.
     chromeos::WallpaperManager::Get()->ResizeAndSaveWallpaper(
         wallpaper,
         file_path.InsertBeforeExtension(chromeos::kSmallWallpaperSuffix),
         ash::CENTER_CROPPED,
         ash::kSmallWallpaperMaxWidth,
         ash::kSmallWallpaperMaxHeight);
   } else {
     BrowserThread::PostTask(
         BrowserThread::UI, FROM_HERE,
         base::Bind(&WallpaperSetWallpaperFunction::OnFailureOrCancel,
-                   this));
+                   this, ""));
+    LOG(ERROR) << "Failed to save downloaded wallpaper.";
   }
 }
 
 void WallpaperSetWallpaperFunction::SetDecodedWallpaper() {
   chromeos::WallpaperManager* wallpaper_manager =
       chromeos::WallpaperManager::Get();
   wallpaper_manager->SetWallpaperFromImageSkia(wallpaper_, layout_);
   bool is_persistent =
       !chromeos::UserManager::Get()->IsCurrentUserEphemeral();
   chromeos::WallpaperInfo info = {
@@ skipping 41 matching lines @@
                                           image_data_.end());
   chromeos::UserImage image(wallpaper, raw_image);
   // In the new wallpaper picker UI, we do not depend on WallpaperDelegate
   // to refresh thumbnail. Uses a null delegate here.
   chromeos::WallpaperManager::Get()->SetCustomWallpaper(
       email_, layout_, chromeos::User::CUSTOMIZED,
       base::WeakPtr<chromeos::WallpaperDelegate>(), image);
   wallpaper_decoder_ = NULL;
   SendResponse(true);
 }
-
-void WallpaperSetCustomWallpaperFunction::OnFailureOrCancel() {
-  wallpaper_decoder_ = NULL;
-  SendResponse(false);
-}