Fix the set_render_frame_proxy_created() bookkeeping in SwapOut.

While investigating issue 794625, I noticed that it is possible for
RFHI::SwapOut to not actually create the proxy.  This happens if (1)
the RFHI to be swapped out is already pending deletion, and (2) the
RFHI to be swapped out is not live.  Nonetheless, the sole caller of
RFHI::SwapOut, RenderFrameHostManager::SwapOutOldFrame, assumes that a
replacement proxy is always created and unconditionally calls
proxy->set_render_frame_proxy_created(true) afterward.  This seems
wrong - instead, the proxy should be set to be live if the IPC to
create it was actually sent, which is what this CL does.

I can't pinpoint any specific issues this might lead to, so this is
more of a speculative/preventative fix for problems in this
area. There's a chance it might be related to issue 794625, though in
that issue, I'd expect the problem to be that we send a message to
create a proxy to a process where the proxy had already been created,
and here, the resulting problems would be from a proxy being marked
as live without actually having been created.

Bug: 794625
Change-Id: I7e3f53c17b541f9d5796714ef7c530a7955cf143
Reviewed-on: https://chromium-review.googlesource.com/1139215
Commit-Queue: Charlie Reis <creis@chromium.org>
Reviewed-by: Charlie Reis <creis@chromium.org>
Cr-Commit-Position: refs/heads/master@{#575935}

content/browser/frame_host/render_frame_host_impl.cc

@@ -1919,6 +1919,10 @@ void RenderFrameHostImpl::SwapOut(
         proxy->frame_tree_node()->current_replication_state();
     Send(new FrameMsg_SwapOut(routing_id_, proxy->GetRoutingID(), is_loading,
                               replication_state));
+
+    // Remember that a RenderFrameProxy was created as part of processing the
+    // SwapOut message above.
+    proxy->set_render_frame_proxy_created(true);
   }
 
   if (web_ui())

content/browser/frame_host/render_frame_host_manager.cc

@@ -400,9 +400,6 @@ void RenderFrameHostManager::SwapOutOldFrame(
   // Tell the old RenderFrameHost to swap out and be replaced by the proxy.
   old_render_frame_host->SwapOut(proxy, true);
 
-  // SwapOut creates a RenderFrameProxy, so set the proxy to be initialized.
-  proxy->set_render_frame_proxy_created(true);
-
   // |old_render_frame_host| will be deleted when its SwapOut ACK is received,
   // or when the timer times out, or when the RFHM itself is deleted (whichever
   // comes first).