[Extensions Cleanup] Combine ExtensionHostQueue, SerialExtensionHostQueue

SerialExtensionHostQueue is now the only implementation of
ExtensionHostQueue. Combine them into a de-virtualized
ExtensionHostQueue.

TBR=halliwell@chromium.org (trivial //chromecast change)

Bug: 1028334
Change-Id: I214596d57ccc1edbd6ba4e9ece266b7845baa954
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1934265
Commit-Queue: Devlin <rdevlin.cronin@chromium.org>
Reviewed-by: Karan Bhatia <karandeepb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#718919}

chrome/browser/extensions/chrome_extension_host_delegate.cc

@@ -20,8 +20,8 @@
 #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"
-#include "extensions/browser/serial_extension_host_queue.h"
 
 namespace extensions {
 
@@ -90,7 +90,7 @@ bool ChromeExtensionHostDelegate::CheckMediaAccessPermission(
 }
 
 ExtensionHostQueue* ChromeExtensionHostDelegate::GetExtensionHostQueue() const {
-  static base::NoDestructor<SerialExtensionHostQueue> queue;
+  static base::NoDestructor<ExtensionHostQueue> queue;
   return queue.get();
 }
 

chromecast/browser/extensions/cast_extension_host_delegate.cc

@@ -8,8 +8,8 @@
 #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"
-#include "extensions/browser/serial_extension_host_queue.h"
 
 namespace extensions {
 
@@ -59,7 +59,7 @@ bool CastExtensionHostDelegate::CheckMediaAccessPermission(
 }
 
 ExtensionHostQueue* CastExtensionHostDelegate::GetExtensionHostQueue() const {
-  static base::NoDestructor<SerialExtensionHostQueue> queue;
+  static base::NoDestructor<ExtensionHostQueue> queue;
   return queue.get();
 }
 

extensions/browser/BUILD.gn

@@ -146,6 +146,7 @@ jumbo_source_set("browser_sources") {
     "extension_host.h",
     "extension_host_delegate.h",
     "extension_host_observer.h",
+    "extension_host_queue.cc",
     "extension_host_queue.h",
     "extension_icon_image.cc",
     "extension_icon_image.h",
@@ -318,8 +319,6 @@ jumbo_source_set("browser_sources") {
     "sandboxed_unpacker.h",
     "script_executor.cc",
     "script_executor.h",
-    "serial_extension_host_queue.cc",
-    "serial_extension_host_queue.h",
     "service_worker/worker_id.cc",
     "service_worker/worker_id.h",
     "service_worker/worker_id_set.cc",

extensions/browser/serial_extension_host_queue.cc → extensions/browser/extension_host_queue.cc

@@ -2,7 +2,9 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "extensions/browser/serial_extension_host_queue.h"
+#include "extensions/browser/extension_host_queue.h"
+
+#include <algorithm>
 
 #include "base/bind.h"
 #include "base/location.h"
@@ -20,6 +22,7 @@ namespace {
 // Gets the number of milliseconds to delay between loading ExtensionHosts. By
 // default this is 0, but it can be overridden by field trials.
 int GetDelayMs() {
+  // TODO(devlin): I think these field trials are dead. Confirm, and remove.
   // A sanity check for the maximum delay, to guard against a bad field trial
   // config being pushed that delays loading too much (e.g. using wrong units).
   static const int kMaxDelayMs = 30 * 1000;
@@ -42,34 +45,33 @@ int GetDelayMs() {
 
 }  // namespace
 
-SerialExtensionHostQueue::SerialExtensionHostQueue() : pending_create_(false) {}
+ExtensionHostQueue::ExtensionHostQueue() : pending_create_(false) {}
 
-SerialExtensionHostQueue::~SerialExtensionHostQueue() {
-}
+ExtensionHostQueue::~ExtensionHostQueue() = default;
 
-void SerialExtensionHostQueue::Add(DeferredStartRenderHost* host) {
+void ExtensionHostQueue::Add(DeferredStartRenderHost* host) {
   queue_.push_back(host);
   PostTask();
 }
 
-void SerialExtensionHostQueue::Remove(DeferredStartRenderHost* host) {
+void ExtensionHostQueue::Remove(DeferredStartRenderHost* host) {
   auto it = std::find(queue_.begin(), queue_.end(), host);
   if (it != queue_.end())
     queue_.erase(it);
 }
 
-void SerialExtensionHostQueue::PostTask() {
+void ExtensionHostQueue::PostTask() {
   if (!pending_create_) {
     base::ThreadTaskRunnerHandle::Get()->PostDelayedTask(
         FROM_HERE,
-        base::BindOnce(&SerialExtensionHostQueue::ProcessOneHost,
+        base::BindOnce(&ExtensionHostQueue::ProcessOneHost,
                        ptr_factory_.GetWeakPtr()),
         base::TimeDelta::FromMilliseconds(GetDelayMs()));
     pending_create_ = true;
   }
 }
 
-void SerialExtensionHostQueue::ProcessOneHost() {
+void ExtensionHostQueue::ProcessOneHost() {
   pending_create_ = false;
   if (queue_.empty())
     return;  // can happen on shutdown

extensions/browser/extension_host_queue.h

@@ -5,22 +5,48 @@
 #ifndef EXTENSIONS_BROWSER_EXTENSION_HOST_QUEUE_H_
 #define EXTENSIONS_BROWSER_EXTENSION_HOST_QUEUE_H_
 
-namespace extensions {
+#include <list>
+
+#include "base/memory/weak_ptr.h"
 
+namespace extensions {
 class DeferredStartRenderHost;
 
-// An interface for a queue of ExtensionHosts waiting for initialization.
-// This is used to implement different throttling strategies.
+// A queue of ExtensionHosts waiting for initialization. This initializes
+// DeferredStartRenderHosts in the order they're Add()ed, with simple rate
+// limiting logic that re-posts each task to the UI thread, to avoid clogging it
+// for a long period of time.
 class ExtensionHostQueue {
  public:
-  virtual ~ExtensionHostQueue() {}
+  ExtensionHostQueue();
+  ~ExtensionHostQueue();
+
+  ExtensionHostQueue(const ExtensionHostQueue& queue) = delete;
+  ExtensionHostQueue& operator=(const ExtensionHostQueue& queue) = delete;
 
   // Adds a host to the queue for RenderView creation.
-  virtual void Add(DeferredStartRenderHost* host) = 0;
+  void Add(DeferredStartRenderHost* host);
 
   // Removes a host from the queue (for example, it may be deleted before
-  // having a chance to start).
-  virtual void Remove(DeferredStartRenderHost* host) = 0;
+  // having a chance to start)
+  void Remove(DeferredStartRenderHost* host);
+
+ private:
+  // Queues up a delayed task to process the next DeferredStartRenderHost in
+  // the queue.
+  void PostTask();
+
+  // Creates the RenderView for the next host in the queue.
+  void ProcessOneHost();
+
+  // True if this queue is currently in the process of starting an
+  // DeferredStartRenderHost.
+  bool pending_create_;
+
+  // The list of DeferredStartRenderHosts waiting to be started.
+  std::list<DeferredStartRenderHost*> queue_;
+
+  base::WeakPtrFactory<ExtensionHostQueue> ptr_factory_{this};
 };
 
 }  // namespace extensions

extensions/browser/serial_extension_host_queue.h

-// Copyright 2015 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#ifndef EXTENSIONS_BROWSER_SERIAL_EXTENSION_HOST_QUEUE_H_
-#define EXTENSIONS_BROWSER_SERIAL_EXTENSION_HOST_QUEUE_H_
-
-#include <list>
-
-#include "base/macros.h"
-#include "base/memory/weak_ptr.h"
-#include "extensions/browser/extension_host_queue.h"
-
-namespace extensions {
-
-class DeferredStartRenderHost;
-
-// An ExtensionHostQueue which initializes DeferredStartRenderHosts in the order
-// they're Add()ed, with simple rate limiting logic that re-posts each task to
-// the UI thread, to avoid clogging it for a long period of time.
-class SerialExtensionHostQueue : public ExtensionHostQueue {
- public:
-  SerialExtensionHostQueue();
-  ~SerialExtensionHostQueue() override;
-
- private:
-  // ExtensionHostQueue:
-  void Add(DeferredStartRenderHost* host) override;
-  void Remove(DeferredStartRenderHost* host) override;
-
-  // Queues up a delayed task to process the next DeferredStartRenderHost in
-  // the queue.
-  void PostTask();
-
-  // Creates the RenderView for the next host in the queue.
-  void ProcessOneHost();
-
-  // True if this queue is currently in the process of starting an
-  // DeferredStartRenderHost.
-  bool pending_create_;
-
-  // The list of DeferredStartRenderHosts waiting to be started.
-  std::list<DeferredStartRenderHost*> queue_;
-
-  base::WeakPtrFactory<SerialExtensionHostQueue> ptr_factory_{this};
-
-  DISALLOW_COPY_AND_ASSIGN(SerialExtensionHostQueue);
-};
-
-}  // namespace extensions
-
-#endif  // EXTENSIONS_BROWSER_SERIAL_EXTENSION_HOST_QUEUE_H_

extensions/shell/browser/shell_extension_host_delegate.cc

@@ -7,8 +7,8 @@
 #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/browser/serial_extension_host_queue.h"
 #include "extensions/shell/browser/shell_extension_web_contents_observer.h"
 
 namespace extensions {
@@ -65,7 +65,7 @@ bool ShellExtensionHostDelegate::CheckMediaAccessPermission(
   return true;
 }
 
-static base::LazyInstance<SerialExtensionHostQueue>::DestructorAtExit g_queue =
+static base::LazyInstance<ExtensionHostQueue>::DestructorAtExit g_queue =
     LAZY_INSTANCE_INITIALIZER;
 
 ExtensionHostQueue* ShellExtensionHostDelegate::GetExtensionHostQueue() const {