Revert r235502 "Add a full screen virtual keyboard to virtual keyboard root window"

Test has been failing on Win8 Aura since it landed.

[ RUN      ] VirtualKeyboardWindowControllerTest.VirtualKeyboardWindowTest
[1816:612:1115/193527:1412105:FATAL:display_manager.cc(571)] Check failed: 1u == updated_display_info_list.size() (1 vs. 2)Multiple display test does not work on Win8 bots. Please skip (don't disable) the test using SupportsMultipleDisplays()
Backtrace:
        base::debug::StackTrace::StackTrace [0x6C8EBBF1+33]
        logging::LogMessage::~LogMessage [0x6C71D2FE+94]
        ash::internal::DisplayManager::UpdateDisplays [0x5BA229F5+293]
        ash::internal::DisplayManager::OnNativeDisplaysChanged [0x5BA22173+2723]
        ash::internal::DisplayManager::InitFromCommandLine [0x5BA1E281+817]
        ash::Shell::Init [0x5B7628A2+210]
        ash::Shell::CreateInstance [0x5B75C8D9+361]
        ash::test::AshTestHelper::SetUp [0x01782E29+281]
        ash::test::AshTestBase::SetUp [0x017753AC+332]
        ash::test::VirtualKeyboardWindowControllerTest::SetUp [0x016A57D7+247]
        testing::internal::HandleExceptionsInMethodIfSupported<testing::Test,void> [0x0174E3BF+319]
        testing::Test::Run [0x01738DDB+107]
        testing::TestInfo::Run [0x017397ED+221]
        testing::TestCase::Run [0x01739F9F+239]
        testing::internal::UnitTestImpl::RunAllTests [0x017408ED+701]
        testing::internal::HandleExceptionsInMethodIfSupported<testing::internal::UnitTestImpl,bool> [0x0174EFE7+327]
        testing::UnitTest::Run [0x0173F150+192]
        base::TestSuite::Run [0x0172DD00+240]
        main [0x01647767+103]
        __tmainCRTStartup [0x018B870F+447] (f:\dd\vctools\crt_bld\self_x86\crt\src\crtexe.c:555)
        mainCRTStartup [0x018B853F+15] (f:\dd\vctools\crt_bld\self_x86\crt\src\crtexe.c:371)
        BaseThreadInitThunk [0x750D8543+14]
        RtlInitializeExceptionChain [0x775DAC69+133]
        RtlInitializeExceptionChain [0x775DAC3C+88]

http://build.chromium.org/p/chromium.win/builders/Win8%20Aura/builds/12680/steps/ash_unittests/logs/stdio

BUG=310331
TBR=bshe@chromium.org

Review URL: https://codereview.chromium.org/74693002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235520 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235520