Enable basic IME functionality under Ash on Windows

With this CL, IMEs become functional under Ash environment on Windows.
Some optional features for Chromium internal use (e.g., IME popup window detection, RTL language detection) will be covered by subsequent CLs.

DesignDoc:
https://docs.google.com/a/chromium.org/document/d/14TBE0LoamQz_MImcNWzeTIW_lo5EUrLJwNwmCi20V1o/edit#

Note:
In this CL, ui/base/ime/win/tsf_text_store.* is not moved but copied to win8/metro_driver/ime/text_store.* in order not to break non-Aura build.  That said, hereafter we will use win8/metro_driver/ime/text_store.* as primary implementation of TSF TextStore.  Anyway, ui/base/ime/win/tsf_text_store.* will be removed when Aura transition is successfully completed.
I also found some style issues in win8/metro_driver/ime/text_store.cc but I'd like to fix them in subsequent CLs to keep this CL as minimum as possible.

BUG=164964
TEST=manually done on Windows 8.1

Review URL: https://codereview.chromium.org/83233002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@238921 0039d316-1c4b-4281-b951-d872f2087c98
14 files changed