Makes construction of (ash)RemoteWindowTreeHostWin explicit

I need to do this as I need to pass in state to the constructor and I
can't do that with lazy construction. This makes creation a little
saner anyway.

I'm not happy about the static setting the HWND. I'll see if I can
clean that up later.

BUG=none
TEST=none
[email protected]

Review URL: https://codereview.chromium.org/277753002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@270747 0039d316-1c4b-4281-b951-d872f2087c98
31 files changed