Reduce temporal coupling of RenderWidgetHostImpl and RenderViewHostImpl init.

Prior work has already detangled a lot of RenderWidgetHostImpl and
RenderViewHostImpl. Moving the registration of the RenderViewHostImpl
with the RenderWidgetHostImpl as late as possible in the construction
sequence further decouples the two classes.

This is preparation for moving RWHI ownership to RenderFrameHost.

Bug: 545684
Change-Id: I5a21a60d1eaeb77fe0270bc2506248162405fb37
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1808184Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Albert J. Wong <ajwong@chromium.org>
Cr-Commit-Position: refs/heads/master@{#697085}

content/browser/renderer_host/render_view_host_impl.cc

@@ -237,8 +237,6 @@ RenderViewHostImpl::RenderViewHostImpl(
   CHECK(result.second) << "Inserting a duplicate item!";
   GetProcess()->AddRoute(routing_id_, this);
 
-  GetWidget()->set_owner_delegate(this);
-
   GetProcess()->AddObserver(this);
   ui::GpuSwitchingManager::GetInstance()->AddObserver(this);
 
@@ -255,6 +253,8 @@ RenderViewHostImpl::RenderViewHostImpl(
       &RenderViewHostImpl::ClosePageTimeout, weak_factory_.GetWeakPtr())));
 
   input_device_change_observer_.reset(new InputDeviceChangeObserver(this));
+
+  GetWidget()->set_owner_delegate(this);
 }
 
 RenderViewHostImpl::~RenderViewHostImpl() {