Revert "Fix app window titlebar blending with direct composition"

This reverts commit 5ad4e08d15110e8212fae941d4638e2e4df7e4c1.

Reason for revert: crbug.com/918461

Original change's description:
> Fix app window titlebar blending with direct composition
>
> Clear the DWM frame area on WM_ERASEBKGND so that Chrome's client area
> blends with DWM frame for app windows.  Refactor the code to update and
> clear DWM frame and move it to hwnd message handler so that browser and
> app windows can share the same code.
>
> This mimics existing logic for updating the DWM frame and adds the clear
> DWM frame behavior to app windows, but one notable change is that it
> will clear on every WM_ERASEBKGND message, and not just the first one.
> This shouldn't have a performance impact and seems more correct anyway.
>
> Bug: 904322
> Change-Id: I70c3ae97a94114dd63110736a35cef4dd887b1aa
> Reviewed-on: https://chromium-review.googlesource.com/c/1382928
> Reviewed-by: Scott Violet <sky@chromium.org>
> Reviewed-by: Bret Sepulveda <bsep@chromium.org>
> Commit-Queue: Sunny Sachanandani <sunnyps@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#618684}

TBR=sky@chromium.org,sunnyps@chromium.org,bsep@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 904322,918461
Change-Id: I681f37f264884cdfab7425eadfbd6c26bbf2d953
Reviewed-on: https://chromium-review.googlesource.com/c/1407602
Commit-Queue: Zhenyao Mo <zmo@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#622168}
9 files changed