Check status on initialize & shutdown the CQ

* If gRPC initialize failed we don't have a connection to begin with so
can't call Read().
* Shutdown the CompletionQueue otherwise the thread won't exit.

Bug: b/142400443
Test: internal unittests
Change-Id: Ifc2a13e36bbdc640908ca1069afed855fc8cd790
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1867313
Commit-Queue: Daniel Nicoara <dnicoara@chromium.org>
Auto-Submit: Daniel Nicoara <dnicoara@chromium.org>
Reviewed-by: Alex Sakhartchouk <alexst@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707463}

chromecast/browser/webview/webview_grpc_service.cc

@@ -138,6 +138,12 @@ void WebviewRpcInstance::ProcessRequestOnWebviewThread(
 }
 
 void WebviewRpcInstance::InitComplete(bool ok) {
+  if (!ok) {
+    destroying_ = true;
+    delete this;
+    return;
+  }
+
   request_ = std::make_unique<webview::WebviewRequest>();
   io_.Read(request_.get(), &read_callback_);
 
@@ -263,6 +269,7 @@ WebviewAsyncService::WebviewAsyncService(
 }
 
 WebviewAsyncService::~WebviewAsyncService() {
+  cq_->Shutdown();
   base::PlatformThread::Join(rpc_thread_);
 }