Revert of Create a unified UIElement interface for Widget, View and Window. (patchset #21 id:1020001 of https://codereview.chromium.org/2776543002/ )

Reason for revert:
Fails to compile on ChromiumOS x86-generic Compile
with error:

[903/7505] CXX obj/ash/ash/ui_element.o
FAILED: obj/ash/ash/ui_element.o
/b/c/goma_client/gomacc i686-pc-linux-gnu-g++ -B/b/c/b/ChromiumOS_x86_generic_Compile/.cros_cache/chrome-sdk/tarballs/x86-generic+9536.0.0+target_toolchain/usr/x86_64-pc-linux-gnu/i686-pc-linux-gnu/binutils-bin/2.25.51-gold -MMD -MF obj/ash/ash/ui_element.o.d -DASH_IMPLEMENTATION -DV8_DEPRECATION_WARNINGS -DUSE_UDEV -DUSE_ASH=1 -DUSE_AURA=1 -DUSE_NSS_CERTS=1 -DUSE_OZONE=1 -DFULL_SAFE_BROWSING -DSAFE_BROWSING_CSD -DSAFE_BROWSING_DB_LOCAL -DCHROMIUM_BUILD -DFIELDTRIAL_TESTING_ENABLED -D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D_FORTIFY_SOURCE=2 -DOS_CHROMEOS -DNDEBUG -DNVALGRIND -DDYNAMIC_ANNOTATIONS_ENABLED=0 -DUSE_EGL -DTOOLKIT_VIEWS=1 -DU_USING_ICU_NAMESPACE=0 -DU_ENABLE_DYLOAD=0 -DU_STATIC_IMPLEMENTATION -DICU_UTIL_DATA_IMPL=ICU_UTIL_DATA_FILE -DUCHAR_TYPE=uint16_t -DSK_IGNORE_LINEONLY_AA_CONVEX_PATH_OPTS -DSK_HAS_PNG_LIBRARY -DSK_HAS_WEBP_LIBRARY -DSK_HAS_JPEG_LIBRARY -DSK_SUPPORT_GPU=1 -DGOOGLE_PROTOBUF_NO_RTTI -DGOOGLE_PROTOBUF_NO_STATIC_INITIALIZER -DHAVE_PTHREAD -DMESA_EGL_NO_X11_HEADERS -I../.. -Igen -I../../third_party/libwebp -I../../third_party/khronos -I../../gpu -I../../third_party/ced/src -I../../third_party/icu/source/common -I../../third_party/icu/source/i18n -I../../skia/config -I../../skia/ext -I../../third_party/skia/include/c -I../../third_party/skia/include/config -I../../third_party/skia/include/core -I../../third_party/skia/include/effects -I../../third_party/skia/include/encode -I../../third_party/skia/include/images -I../../third_party/skia/include/lazy -I../../third_party/skia/include/pathops -I../../third_party/skia/include/pdf -I../../third_party/skia/include/pipe -I../../third_party/skia/include/ports -I../../third_party/skia/include/utils -I../../third_party/skia/third_party/vulkan -I../../third_party/skia/include/gpu -I../../third_party/skia/src/gpu -I../../third_party/skia/src/sksl -I/b/c/b/ChromiumOS_x86_generic_Compile/.cros_cache/chrome-sdk/tarballs/x86-generic+9536.0.0+sysroot_chromeos-base_chromeos-chrome.tar.xz/usr/include/dbus-1.0 -I/b/c/b/ChromiumOS_x86_generic_Compile/.cros_cache/chrome-sdk/tarballs/x86-generic+9536.0.0+sysroot_chromeos-base_chromeos-chrome.tar.xz/usr/lib/dbus-1.0/include -I../../third_party/protobuf/src -Igen/protoc_out -I../../third_party/protobuf/src -I../../third_party/libwebm/source -I../../third_party/boringssl/src/include -I/b/c/b/ChromiumOS_x86_generic_Compile/.cros_cache/chrome-sdk/tarballs/x86-generic+9536.0.0+sysroot_chromeos-base_chromeos-chrome.tar.xz/usr/include/nss -I/b/c/b/ChromiumOS_x86_generic_Compile/.cros_cache/chrome-sdk/tarballs/x86-generic+9536.0.0+sysroot_chromeos-base_chromeos-chrome.tar.xz/usr/include/nspr -I../../third_party/WebKit -Igen/third_party/WebKit -I../../v8/include -Igen/v8/include -I../../third_party/qcms/src -Igen -I../../third_party/mesa/src/include -fno-strict-aliasing -Wno-builtin-macro-redefined -D__DATE__= -D__TIME__= -D__TIMESTAMP__= -funwind-tables -fPIC -pipe -B../../third_party/binutils/Linux_x64/Release/bin -m32 -msse2 -mfpmath=sse -mmmx -pthread -Wall -Werror -Wno-unused-local-typedefs -Wno-maybe-uninitialized -Wno-missing-field-initializers -Wno-unused-parameter -O2 -fno-ident -fdata-sections -ffunction-sections -fno-omit-frame-pointer -g2 -gsplit-dwarf --sysroot=../../../.cros_cache/chrome-sdk/tarballs/x86-generic+9536.0.0+sysroot_chromeos-base_chromeos-chrome.tar.xz -fvisibility=hidden -std=gnu++11 -Wno-narrowing -fno-rtti -fno-exceptions -fvisibility-inlines-hidden -march=i686 -pipe -march=i686 -pipe -pipe -march=i686 -mfpmath=sse -mmmx -msse -msse2 -msse3 -D__google_stl_debug_vector=1 -c ../../ash/devtools/ui_element.cc -o obj/ash/ash/ui_element.o
../../ash/devtools/ui_element.cc: In member function 'std::string ash::devtools::UIElement::GetTypeName() const':
../../ash/devtools/ui_element.cc:37:1: error: control reaches end of non-void function [-Werror=return-type]
 }
 ^
cc1plus.elf: all warnings being treated as errors

Original issue's description:
> Create a unified UIElement interface for Widget, View and Window.
>
> The unified interface will enable css_agent to set/access many
> properties of widget, view and window without the need of knowing the
> actual object type. A UIElement tree where each node can be either
> view, widget and window will be kept in sync with tree structures of
> window, widget and view objects.
>
> BUG=700024
>
> Review-Url: https://codereview.chromium.org/2776543002
> Cr-Commit-Position: refs/heads/master@{#473315}
> Committed: https://chromium.googlesource.com/chromium/src/+/bdcdb17a4fa7ffea34afed460b776cc2e5032855

TBR=sadrul@chromium.org,thanhph@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=700024

Review-Url: https://codereview.chromium.org/2899503002
Cr-Commit-Position: refs/heads/master@{#473331}
15 files changed