[MBI] Change SetUpMojoIfNeeded to DCHECK.

The various AgentSchedulingGroupHost::Create* methods assume that the
caller already called InitProcessAndMojos, so there is no need to call
SetUpMojoIfNeeded from them. Instead, replace it with DCHECKs to make
sure the process is initialized and the mojo remote is bound.

Bug: 1111231
Change-Id: I95736b806adaabceae560131dd2a816dfc614f95
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2437993Reviewed-by: Kouhei Ueno <kouhei@chromium.org>
Reviewed-by: Alex Moshchuk <alexmos@chromium.org>
Reviewed-by: Dominic Farolino <dom@chromium.org>
Commit-Queue: Tal Pressman <talp@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813051}

content/browser/renderer_host/agent_scheduling_group_host.cc

@@ -240,12 +240,14 @@ mojom::RouteProvider* AgentSchedulingGroupHost::GetRemoteRouteProvider() {
 }
 
 void AgentSchedulingGroupHost::CreateFrame(mojom::CreateFrameParamsPtr params) {
-  SetUpMojoIfNeeded();
+  DCHECK(process_.IsInitializedAndNotDead());
+  DCHECK(mojo_remote_.is_bound());
   mojo_remote_.get()->CreateFrame(std::move(params));
 }
 
 void AgentSchedulingGroupHost::CreateView(mojom::CreateViewParamsPtr params) {
-  SetUpMojoIfNeeded();
+  DCHECK(process_.IsInitializedAndNotDead());
+  DCHECK(mojo_remote_.is_bound());
   mojo_remote_.get()->CreateView(std::move(params));
 }