Revert 245802 "WallpaperLoader should inform caller that load re..."

Broke interactive_ui_tests on Linux ChromiumOS Tests:
http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Tests%20%28dbg%29%283%29/builds/32619/steps/interactive_ui_tests/logs/UseMigratedWallpaperInfo

[26595:26595:0119/124449:30256177955:FATAL:wallpaper_manager.cc(236)] Check failed: BrowserThread::CurrentlyOn(BrowserThread::UI).
 [0x7f741f468504] base::debug::StackTrace::StackTrace()
 [0x7f741f4d6523] logging::LogMessage::~LogMessage()
 [0x00000324a0a8] chromeos::WallpaperManager::PendingWallpaper::OnWallpaperSet()
 [0x00000325bde6] base::internal::RunnableAdapter\u003C>::Run()
 [0x000003259599] base::internal::InvokeHelper\u003C>::MakeItSo()
 [0x00000325612b] base::internal::Invoker\u003C>::Run()
 [0x000000b25601] base::Callback\u003C>::Run()
 [0x00000325076d] chromeos::MovableOnDestroyCallback::~MovableOnDestroyCallback()
 [0x000003252f54] base::DefaultDeleter\u003C>::operator()()
 [0x000003250ba2] base::internal::scoped_ptr_impl\u003C>::~scoped_ptr_impl()
 [0x0000032507be] scoped_ptr\u003C>::~scoped_ptr()
 [0x000003250930] base::internal::PassedWrapper\u003C>::~PassedWrapper()
 [0x00000325edf2] base::internal::BindState\u003C>::~BindState()
 [0x00000325ee40] base::internal::BindState\u003C>::~BindState()
 [0x7f741f41db61] base::RefCountedThreadSafe\u003C>::DeleteInternal()
 [0x7f741f41d41b] base::DefaultRefCountedThreadSafeTraits\u003C>::Destruct()
 [0x7f741f41cc88] base::RefCountedThreadSafe\u003C>::Release()
 [0x7f741f457afb] scoped_refptr\u003C>::~scoped_refptr()
 [0x7f741f457a92] base::internal::CallbackBase::~CallbackBase()
 [0x00000321f3a4] base::Callback\u003C>::~Callback()
 [0x0000034445de] base::internal::BindState\u003C>::~BindState()
 [0x00000344461c] base::internal::BindState\u003C>::~BindState()
 [0x7f741f41db61] base::RefCountedThreadSafe\u003C>::DeleteInternal()
 [0x7f741f41d41b] base::DefaultRefCountedThreadSafeTraits\u003C>::Destruct()
 [0x7f741f41cc88] base::RefCountedThreadSafe\u003C>::Release()
 [0x7f741f457afb] scoped_refptr\u003C>::~scoped_refptr()
 [0x7f741f457a92] base::internal::CallbackBase::~CallbackBase()
 [0x7f741f43a338] base::Callback\u003C>::~Callback()
 [0x7f741f538342] base::PendingTask::~PendingTask()
 [0x7f741f4f6201] base::MessageLoop::DeletePendingTasks()
 [0x7f741f4f4788] base::MessageLoop::~MessageLoop()
 [0x7f74156f263c] base::MessageLoopForUI::~MessageLoopForUI()
 [0x7f74156f266e] base::MessageLoopForUI::~MessageLoopForUI()
 [0x7f74156efd5a] base::DefaultDeleter\u003C>::operator()()
 [0x7f74156ee9a8] base::internal::scoped_ptr_impl\u003C>::~scoped_ptr_impl()
 [0x7f74156ee524] scoped_ptr\u003C>::~scoped_ptr()
 [0x7f74156e8857] content::BrowserMainLoop::~BrowserMainLoop()
 [0x7f74156e888c] content::BrowserMainLoop::~BrowserMainLoop()
 [0x7f74156f35e6] base::DefaultDeleter\u003C>::operator()()
 [0x7f74156f36a7] base::internal::scoped_ptr_impl\u003C>::reset()
 [0x7f74156f3479] scoped_ptr\u003C>::reset()
 [0x7f74156f333c] content::BrowserMainRunnerImpl::Shutdown()
 [0x7f74156e6d46] content::BrowserMain()
 [0x00000376384c] content::BrowserTestBase::SetUp()
 [0x000001c5b554] InProcessBrowserTest::SetUp()

BUG=333809
TBR=alemate@chromium.org

Review URL: https://codereview.chromium.org/142593003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245842 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245842
content: Copy plugin code from Blink to Chromium.

This just copy the source files, no gyp changes at this moment, this
will come next.

BUG=331302
TEST=None
R=jochen@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/135133003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245843 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245843