Fix ScreenLockerTest. Check whether bitmap is valid.

chrome/browser/ui/webui/options2/chromeos/wallpaper_source.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/ui/webui/options2/chromeos/wallpaper_source.h"
 
 #include "ash/desktop_background/desktop_background_controller.h"
 #include "ash/shell.h"
 #include "base/debug/trace_event.h"
 #include "base/synchronization/cancellation_flag.h"
@@ skipping 39 matching lines @@
 
   int request_id() {
     return request_id_;
   }
 
   void EncodeWallpaper() {
     if (cancel_flag_.IsSet())
       return;
     TRACE_EVENT0("LOCK_SCREEN", "imageEncoding");
     SkAutoLockPixels lock_input(image_);
+
+    if (!image_.readyToDraw())
+      return;
+
     // Avoid compression to make things faster.
     gfx::PNGCodec::EncodeWithCompressionLevel(
         reinterpret_cast<unsigned char*>(image_.getAddr32(0, 0)),
         gfx::PNGCodec::FORMAT_SkBitmap,
         gfx::Size(image_.width(), image_.height()),
         image_.width() * image_.bytesPerPixel(),
         false,
         std::vector<gfx::PNGCodec::Comment>(),
         Z_NO_COMPRESSION,
         &data_->data());
@@ skipping 100 matching lines @@
 
 void WallpaperImageSource::SendCurrentUserWallpaper(int request_id,
     scoped_refptr<base::RefCountedBytes> data) {
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
   SendResponse(request_id, data);
   TRACE_EVENT_ASYNC_END0("SCREEN_LOCK", "GetUserWallpaper", request_id);
 }
 
 }  // namespace options2
 }  // namespace chromeos