Revert "Make browser process own RenderView."

This reverts commit 55bc919aff4f9d30d03090859321050557407e85.

Reason for revert: Suspected cause of https://crbug.com/990192

Since this changes the ownership of RenderWidget and the newly flaky
test (which started failing on MSAN 1 build after this landed) has a
use-after-free in RenderWidget, I am suspecting this CL.

Original change's description:
> Make browser process own RenderView.
> 
> Historically, RenderView and RenderWidget were 1:1, and their lifetimes were
> entwined.
> 1) RenderViewHost would create the RenderView.
> 2) RenderView would create a RenderWidget and pass ownership of itself to the
> RenderWidget.
> 3) RenderViewHost's destructor would destroy the RenderWidget, thus destroying
> the RenderView
> 
> We want the lifetime of RenderView and RenderWidget to be decoupled. The first
> step of this is making RenderView explicitly owned by the browser. This means
> that instead of (3), RenderViewHost's destructor will destroy the RenderView,
> which will in turn destroy the RenderWidget.
> 
> One subtlety is that prior to this CL, RenderWidget was always destroyed
> asynchronously. The original reason for supporting this -- dealing with
> re-entrancy from nested message loops -- is no longer applicable. The IPC that
> destroys RenderWidget is asynchronous, which means it can never be called from a
> re-entrant context. However, it is possible for a RenderWidget associated with a
> child-frame to be synchronously destroyed by JS. This can be re-entrant. This CL
> updates destruction of RenderWidget to be synchronous when called from IPC.
> 
> Bug: 987731
> Change-Id: If4b319fab19d02c5495ba14e5cc929f441ca4d2e
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1717456
> Commit-Queue: Avi Drissman <avi@chromium.org>
> Reviewed-by: Avi Drissman <avi@chromium.org>
> Reviewed-by: Daniel Cheng <dcheng@chromium.org>
> Auto-Submit: Erik Chen <erikchen@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#683247}

TBR=avi@chromium.org,dcheng@chromium.org,erikchen@chromium.org

Change-Id: I762230d0df57c6bcd75af80c1aa231d7b4d2183e
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 987731, 990192
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1731991
Reviewed-by: Matt Giuca <mgiuca@chromium.org>
Commit-Queue: Matt Giuca <mgiuca@chromium.org>
Cr-Commit-Position: refs/heads/master@{#683457}
15 files changed