Suppress uninitialized read of ui::NativeTheme::ExtraParams.scrollbar_track.is_upper

BUG=374410
TBR=sky@chromium.org

Review URL: https://codereview.chromium.org/298643004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@271753 0039d316-1c4b-4281-b951-d872f2087c98

tools/valgrind/drmemory/suppressions_full.txt

@@ -2173,3 +2173,8 @@ gpu.dll!gpu::gles2::ShaderTranslator::GetStringForOptionsThatWouldEffectCompilat
 UNINITIALIZED READ
 name=bug_375401
 *!ToolbarOriginChipView::Update
+
+UNINITIALIZED READ
+name=374410
+*!ui::NativeThemeWin::PaintScrollbarTrack
+*!ui::NativeThemeWin::PaintDirect