[Extensions Cleanup] Remove ExtensionHostDelegate::GetExtensionHostQueue()

All implementations of ExtensionHostDelegate::GetExtensionHostQueue()
returned a singleton instance of an ExtensionHostQueue. Instead of this
piping, introduce ExtensionHostQueue::GetInstance(), which does the same
thing without needing to be implemented by the embedder.

TBR=atwilson@chromium.org (trivial background_contents.cc change)

Bug: 1028334
Change-Id: I339267c2a8193c27bd782b63a8f8cc5e15957be4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935489
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719395}

chrome/browser/background/background_contents.cc

@@ -84,7 +84,7 @@ BackgroundContents::~BackgroundContents() {
   for (auto& observer : deferred_start_render_host_observer_list_)
     observer.OnDeferredStartRenderHostDestroyed(this);
 
-  extension_host_delegate_->GetExtensionHostQueue()->Remove(this);
+  extensions::ExtensionHostQueue::GetInstance().Remove(this);
 }
 
 const GURL& BackgroundContents::GetURL() const {
@@ -93,7 +93,7 @@ const GURL& BackgroundContents::GetURL() const {
 
 void BackgroundContents::CreateRenderViewSoon(const GURL& url) {
   initial_url_ = url;
-  extension_host_delegate_->GetExtensionHostQueue()->Add(this);
+  extensions::ExtensionHostQueue::GetInstance().Add(this);
 }
 
 void BackgroundContents::CloseContents(WebContents* source) {

chrome/browser/extensions/chrome_extension_host_delegate.cc

@@ -7,7 +7,6 @@
 #include <memory>
 #include <string>
 
-#include "base/no_destructor.h"
 #include "chrome/browser/apps/platform_apps/audio_focus_web_contents_observer.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/chrome_extension_web_contents_observer.h"
@@ -20,7 +19,6 @@
 #include "components/performance_manager/performance_manager_tab_helper.h"
 #include "components/performance_manager/public/performance_manager.h"
 #include "extensions/browser/extension_host.h"
-#include "extensions/browser/extension_host_queue.h"
 #include "extensions/browser/extension_system.h"
 
 namespace extensions {
@@ -89,11 +87,6 @@ bool ChromeExtensionHostDelegate::CheckMediaAccessPermission(
                                    extension);
 }
 
-ExtensionHostQueue* ChromeExtensionHostDelegate::GetExtensionHostQueue() const {
-  static base::NoDestructor<ExtensionHostQueue> queue;
-  return queue.get();
-}
-
 content::PictureInPictureResult
 ChromeExtensionHostDelegate::EnterPictureInPicture(
     content::WebContents* web_contents,

chrome/browser/extensions/chrome_extension_host_delegate.h

@@ -32,7 +32,6 @@ class ChromeExtensionHostDelegate : public ExtensionHostDelegate {
                                   const GURL& security_origin,
                                   blink::mojom::MediaStreamType type,
                                   const Extension* extension) override;
-  ExtensionHostQueue* GetExtensionHostQueue() const override;
   content::PictureInPictureResult EnterPictureInPicture(
       content::WebContents* web_contents,
       const viz::SurfaceId& surface_id,

chromecast/browser/extensions/cast_extension_host_delegate.cc

@@ -5,10 +5,8 @@
 #include "chromecast/browser/extensions/cast_extension_host_delegate.h"
 
 #include "base/logging.h"
-#include "base/no_destructor.h"
 #include "chromecast/browser/extensions/cast_extension_web_contents_observer.h"
 #include "content/public/browser/web_contents_delegate.h"
-#include "extensions/browser/extension_host_queue.h"
 #include "extensions/browser/media_capture_util.h"
 
 namespace extensions {
@@ -58,11 +56,6 @@ bool CastExtensionHostDelegate::CheckMediaAccessPermission(
   return media_capture_util::CheckMediaAccessPermission(type, extension);
 }
 
-ExtensionHostQueue* CastExtensionHostDelegate::GetExtensionHostQueue() const {
-  static base::NoDestructor<ExtensionHostQueue> queue;
-  return queue.get();
-}
-
 content::PictureInPictureResult
 CastExtensionHostDelegate::EnterPictureInPicture(
     content::WebContents* web_contents,

chromecast/browser/extensions/cast_extension_host_delegate.h

@@ -33,7 +33,6 @@ class CastExtensionHostDelegate : public ExtensionHostDelegate {
                                   const GURL& security_origin,
                                   blink::mojom::MediaStreamType type,
                                   const Extension* extension) override;
-  ExtensionHostQueue* GetExtensionHostQueue() const override;
   content::PictureInPictureResult EnterPictureInPicture(
       content::WebContents* web_contents,
       const viz::SurfaceId& surface_id,

extensions/browser/extension_host.cc

@@ -108,7 +108,7 @@ ExtensionHost::~ExtensionHost() {
   // Remove ourselves from the queue as late as possible (before effectively
   // destroying self, but after everything else) so that queues that are
   // monitoring lifetime get a chance to see stop-loading events.
-  delegate_->GetExtensionHostQueue()->Remove(this);
+  ExtensionHostQueue::GetInstance().Remove(this);
 
   // Deliberately stop observing |host_contents_| because its destruction
   // events (like DidStopLoading, it turns out) can call back into
@@ -138,7 +138,7 @@ void ExtensionHost::CreateRenderViewSoon() {
     // to defer.
     CreateRenderViewNow();
   } else {
-    delegate_->GetExtensionHostQueue()->Add(this);
+    ExtensionHostQueue::GetInstance().Add(this);
   }
 }
 

extensions/browser/extension_host_delegate.h

@@ -30,7 +30,6 @@ class SurfaceId;
 namespace extensions {
 class Extension;
 class ExtensionHost;
-class ExtensionHostQueue;
 
 // A delegate to support functionality that cannot exist in the extensions
 // module. This is not an inner class of ExtensionHost to allow it to be forward
@@ -75,10 +74,6 @@ class ExtensionHostDelegate {
       blink::mojom::MediaStreamType type,
       const Extension* extension) = 0;
 
-  // Returns the ExtensionHostQueue implementation to use for creating
-  // ExtensionHost renderers.
-  virtual ExtensionHostQueue* GetExtensionHostQueue() const = 0;
-
   // Notifies the Picture-in-Picture controller that there is a new player
   // entering Picture-in-Picture.
   // Returns the result of the enter request.

extensions/browser/extension_host_queue.cc

@@ -8,6 +8,7 @@
 
 #include "base/bind.h"
 #include "base/location.h"
+#include "base/no_destructor.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ -20,6 +21,12 @@ ExtensionHostQueue::ExtensionHostQueue() : pending_create_(false) {}
 
 ExtensionHostQueue::~ExtensionHostQueue() = default;
 
+// static
+ExtensionHostQueue& ExtensionHostQueue::GetInstance() {
+  static base::NoDestructor<ExtensionHostQueue> queue;
+  return *queue;
+}
+
 void ExtensionHostQueue::Add(DeferredStartRenderHost* host) {
   queue_.push_back(host);
   PostTask();

extensions/browser/extension_host_queue.h

@@ -24,6 +24,9 @@ class ExtensionHostQueue {
   ExtensionHostQueue(const ExtensionHostQueue& queue) = delete;
   ExtensionHostQueue& operator=(const ExtensionHostQueue& queue) = delete;
 
+  // Returns the single global instance of the ExtensionHostQueue.
+  static ExtensionHostQueue& GetInstance();
+
   // Adds a host to the queue for RenderView creation.
   void Add(DeferredStartRenderHost* host);
 

extensions/shell/browser/shell_extension_host_delegate.cc

@@ -4,10 +4,8 @@
 
 #include "extensions/shell/browser/shell_extension_host_delegate.h"
 
-#include "base/lazy_instance.h"
 #include "base/logging.h"
 #include "content/public/browser/web_contents_delegate.h"
-#include "extensions/browser/extension_host_queue.h"
 #include "extensions/browser/media_capture_util.h"
 #include "extensions/shell/browser/shell_extension_web_contents_observer.h"
 
@@ -65,13 +63,6 @@ bool ShellExtensionHostDelegate::CheckMediaAccessPermission(
   return true;
 }
 
-static base::LazyInstance<ExtensionHostQueue>::DestructorAtExit g_queue =
-    LAZY_INSTANCE_INITIALIZER;
-
-ExtensionHostQueue* ShellExtensionHostDelegate::GetExtensionHostQueue() const {
-  return g_queue.Pointer();
-}
-
 content::PictureInPictureResult
 ShellExtensionHostDelegate::EnterPictureInPicture(
     content::WebContents* web_contents,

extensions/shell/browser/shell_extension_host_delegate.h

@@ -33,7 +33,6 @@ class ShellExtensionHostDelegate : public ExtensionHostDelegate {
                                   const GURL& security_origin,
                                   blink::mojom::MediaStreamType type,
                                   const Extension* extension) override;
-  ExtensionHostQueue* GetExtensionHostQueue() const override;
   content::PictureInPictureResult EnterPictureInPicture(
       content::WebContents* web_contents,
       const viz::SurfaceId& surface_id,