Revert "Remove IME surface when occured in multi-window mode"

This reverts commit 460dabda.

Reason for revert: Droidcop-triggered revert due to breakage https://android-build.googleplex.com/builds/quarterdeck?testMethod=testTopPositionSwitchOnTapTimeoutDifferentProcess&testClass=android.server.wm.lifecycle.ActivityLifecycleTopResumedStateTests&atpConfigName=cts%2Fframework%2Fgce-presubmit-wm-cloud-tf-3&testModule=CtsWindowManagerDeviceTestCases&fkbb=6585261&lkbb=6585728&lkgb=6581565&testResults=true&badBuildCount=13&branch=git_rvc-qpr-dev-plus-aosp&target=aosp_cf_x86_phone-userdebug, bug b/158836294

Bug: 158836294
Change-Id: Iec015564030658845a5b1262c23c5b72570af9cf