Remove the private field CastWebContentsImpl::parent_cast_web_contents_, which is unused

Additionally, reenable the warning as the warning shouldn't show up
anywhere else in the build.

Bug: 383016423
Cq-Include-Trybots: luci.chromium.try:linux-cast-x64-rel,linux-cast-x64-dbg
Change-Id: Icdcb0e9877f341504e62cab15f2cedc32774dda9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6115847
Reviewed-by: Nico Weber <thakis@chromium.org>
Auto-Submit: Alan Zhao <ayzhao@google.com>
Commit-Queue: Nico Weber <thakis@chromium.org>
Owners-Override: Nico Weber <thakis@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1399523}

build/config/compiler/BUILD.gn

@@ -1996,11 +1996,6 @@ config("default_warnings") {
         # TODO(crbug.com/376641662): Fix and re-enable.
         cflags += [ "-Wno-nontrivial-memcall" ]
       }
-
-      if (is_castos) {
-        # TODO(crbug.com/383016423): Re-enable.
-        cflags += [ "-Wno-unused-private-field" ]
-      }
     }
 
     # Some builders, such as Cronet, use a different version of Clang than

chromecast/browser/cast_web_contents_impl.cc

@@ -131,13 +131,6 @@ void CastWebContentsImpl::RemoveRenderProcessHostObserver() {
 
 CastWebContentsImpl::CastWebContentsImpl(content::WebContents* web_contents,
                                          mojom::CastWebViewParamsPtr params)
-    : CastWebContentsImpl(web_contents,
-                          std::move(params),
-                          nullptr /* parent */) {}
-
-CastWebContentsImpl::CastWebContentsImpl(content::WebContents* web_contents,
-                                         mojom::CastWebViewParamsPtr params,
-                                         CastWebContents* parent)
     : web_contents_(web_contents),
       params_(std::move(params)),
       page_state_(PageState::IDLE),
@@ -148,7 +141,6 @@ CastWebContentsImpl::CastWebContentsImpl(content::WebContents* web_contents,
                          ? std::make_unique<CastMediaBlocker>(web_contents_)
                          : nullptr),
       main_process_host_(nullptr),
-      parent_cast_web_contents_(parent),
       tab_id_(params_->is_root_window ? 0 : next_tab_id++),
       id_(next_id++),
       main_frame_loaded_(false),
@@ -931,7 +923,7 @@ void CastWebContentsImpl::InnerWebContentsCreated(
   params->enabled_for_dev = params_->enabled_for_dev;
   params->background_color = params_->background_color;
   auto result = inner_contents_.insert(std::unique_ptr<CastWebContentsImpl>(
-      new CastWebContentsImpl(inner_web_contents, std::move(params), this)));
+      new CastWebContentsImpl(inner_web_contents, std::move(params))));
 
   // Notifies remote observers.
   for (auto& observer : observers_) {

chromecast/browser/cast_web_contents_impl.h

@@ -149,10 +149,6 @@ class CastWebContentsImpl : public CastWebContents,
       content::WebContentsObserver::MediaStoppedReason reason) override;
 
  private:
-  // Constructor used to create inner CastWebContents.
-  CastWebContentsImpl(content::WebContents* web_contents,
-                      mojom::CastWebViewParamsPtr params,
-                      CastWebContents* parent);
   void OnPageLoading();
   void OnPageLoaded();
   void UpdatePageState();
@@ -179,7 +175,6 @@ class CastWebContentsImpl : public CastWebContents,
   // Retained so that this observer can be removed before being destroyed:
   content::RenderProcessHost* main_process_host_;
 
-  CastWebContents* const parent_cast_web_contents_ = nullptr;
   base::flat_set<std::unique_ptr<CastWebContents>> inner_contents_;
   base::Value::Dict renderer_features_;