initial support for blocking media autoplay

This adds a setting to chrome://flags to block media autoplay.
Issue #92

Author: octocorvus

patches/0088-initial-support-for-blocking-media-autoplay.patch

@@ -0,0 +1,187 @@
+From 166e8afbf262bd0584b87a6e353a3ed2673cf3bc Mon Sep 17 00:00:00 2001
+From: octocorvus <[email protected]>
+Date: Thu, 6 Oct 2022 20:17:24 +0000
+Subject: [PATCH] initial support for blocking media autoplay
+
+This adds a setting to chrome://flags to block media autoplay.
+Issue #92
+---
+ chrome/browser/about_flags.cc                      |  4 ++++
+ chrome/browser/flag-metadata.json                  |  7 +++++++
+ chrome/browser/flag_descriptions.cc                |  3 +++
+ chrome/browser/flag_descriptions.h                 |  3 +++
+ third_party/blink/common/features.cc               |  3 +++
+ third_party/blink/public/common/features.h         |  2 ++
+ .../renderer/core/html/media/autoplay_policy.cc    | 14 +++++++++++++-
+ .../renderer/core/html/media/autoplay_policy.h     |  2 ++
+ .../renderer/core/html/media/html_media_element.cc |  3 ++-
+ 9 files changed, 39 insertions(+), 2 deletions(-)
+
+diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
+index 91b87e334bb27..5f71846e5347f 100644
+--- a/chrome/browser/about_flags.cc
++++ b/chrome/browser/about_flags.cc
+@@ -6135,6 +6135,10 @@ const FeatureEntry kFeatureEntries[] = {
+      flag_descriptions::kDisableProcessReuseDescription, kOsDesktop,
+      FEATURE_VALUE_TYPE(features::kDisableProcessReuse)},
+ 
++    {"block-media-autoplay", flag_descriptions::kBlockMediaAutoplay,
++     flag_descriptions::kBlockMediaAutoplayDescription, kOsAll,
++     FEATURE_VALUE_TYPE(blink::features::kBlockMediaAutoplay)},
++
+ #if !BUILDFLAG(IS_ANDROID)
+     {"enable-accessibility-live-caption",
+      flag_descriptions::kEnableAccessibilityLiveCaptionName,
+diff --git a/chrome/browser/flag-metadata.json b/chrome/browser/flag-metadata.json
+index 0744e987693b2..2d9d5ec743286 100644
+--- a/chrome/browser/flag-metadata.json
++++ b/chrome/browser/flag-metadata.json
+@@ -1370,6 +1370,13 @@
+       "[email protected]", "[email protected]", "[email protected]" ],
+     "expiry_milestone": 110
+   },
++  {
++    "name": "block-media-autoplay",
++    "owners": [
++      "[email protected]"
++    ],
++    "expiry_milestone": -1
++  },
+   {
+     "name": "disable-quick-answers-v2-translation",
+     "owners": [ "croissant-eng" ],
+diff --git a/chrome/browser/flag_descriptions.cc b/chrome/browser/flag_descriptions.cc
+index 2998fc1683b13..cc30201b5014f 100644
+--- a/chrome/browser/flag_descriptions.cc
++++ b/chrome/browser/flag_descriptions.cc
+@@ -830,6 +830,9 @@ const char kDisableProcessReuseDescription[] =
+     "unrelated tabs. This is an experimental mode that will result in more "
+     "processes being created.";
+ 
++const char kBlockMediaAutoplay[] = "Block media autoplay";
++const char kBlockMediaAutoplayDescription[] = "Block media autoplay.";
++
+ const char kDisallowDocWrittenScriptsUiName[] =
+     "Block scripts loaded via document.write";
+ const char kDisallowDocWrittenScriptsUiDescription[] =
+diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
+index d095089242878..482d9f5673357 100644
+--- a/chrome/browser/flag_descriptions.h
++++ b/chrome/browser/flag_descriptions.h
+@@ -415,6 +415,9 @@ extern const char kDarkLightTestDescription[];
+ extern const char kDisableProcessReuse[];
+ extern const char kDisableProcessReuseDescription[];
+ 
++extern const char kBlockMediaAutoplay[];
++extern const char kBlockMediaAutoplayDescription[];
++
+ extern const char kDiscountConsentV2Name[];
+ extern const char kDiscountConsentV2Description[];
+ 
+diff --git a/third_party/blink/common/features.cc b/third_party/blink/common/features.cc
+index e69f9c7bab3fe..e40c3dd8986ee 100644
+--- a/third_party/blink/common/features.cc
++++ b/third_party/blink/common/features.cc
+@@ -1623,5 +1623,8 @@ const base::Feature kWebRtcThreadsUseResourceEfficientType{
+ const base::Feature kThrottleIntersectionObserverUMA{
+     "ThrottleIntersectionObserverUMA", base::FEATURE_DISABLED_BY_DEFAULT};
+ 
++const base::Feature kBlockMediaAutoplay{"BlockMediaAutoplay",
++                                        base::FEATURE_DISABLED_BY_DEFAULT};
++
+ }  // namespace features
+ }  // namespace blink
+diff --git a/third_party/blink/public/common/features.h b/third_party/blink/public/common/features.h
+index 73ff7dbf3936b..5b9aade655d5c 100644
+--- a/third_party/blink/public/common/features.h
++++ b/third_party/blink/public/common/features.h
+@@ -869,6 +869,8 @@ BLINK_COMMON_EXPORT extern const base::Feature
+ // collected on 10% of animation frames.
+ BLINK_COMMON_EXPORT extern const base::Feature kThrottleIntersectionObserverUMA;
+ 
++BLINK_COMMON_EXPORT extern const base::Feature kBlockMediaAutoplay;
++
+ }  // namespace features
+ }  // namespace blink
+ 
+diff --git a/third_party/blink/renderer/core/html/media/autoplay_policy.cc b/third_party/blink/renderer/core/html/media/autoplay_policy.cc
+index 871d82556706b..59e05e0c595bc 100644
+--- a/third_party/blink/renderer/core/html/media/autoplay_policy.cc
++++ b/third_party/blink/renderer/core/html/media/autoplay_policy.cc
+@@ -4,7 +4,9 @@
+ 
+ #include "third_party/blink/renderer/core/html/media/autoplay_policy.h"
+ 
++#include "base/feature_list.h"
+ #include "build/build_config.h"
++#include "third_party/blink/public/common/features.h"
+ #include "third_party/blink/public/mojom/autoplay/autoplay.mojom-blink.h"
+ #include "third_party/blink/public/mojom/permissions_policy/permissions_policy.mojom-blink.h"
+ #include "third_party/blink/public/mojom/webpreferences/web_preferences.mojom-blink.h"
+@@ -217,6 +219,9 @@ void AutoplayPolicy::StopAutoplayMutedWhenVisible() {
+ 
+ bool AutoplayPolicy::RequestAutoplayUnmute() {
+   DCHECK_NE(0, element_->EffectiveMediaVolume());
++  if (IsAutoplayBlocked())
++    return false;
++
+   bool was_autoplaying_muted = IsAutoplayingMutedInternal(true);
+ 
+   TryUnlockingUserGesture();
+@@ -241,6 +246,9 @@ bool AutoplayPolicy::RequestAutoplayUnmute() {
+ }
+ 
+ bool AutoplayPolicy::RequestAutoplayByAttribute() {
++  if (IsAutoplayBlocked())
++    return false;
++
+   if (!ShouldAutoplay())
+     return false;
+ 
+@@ -267,7 +275,7 @@ absl::optional<DOMExceptionCode> AutoplayPolicy::RequestPlay() {
+   if (!LocalFrame::HasTransientUserActivation(
+           element_->GetDocument().GetFrame())) {
+     autoplay_uma_helper_->OnAutoplayInitiated(AutoplaySource::kMethod);
+-    if (IsGestureNeededForPlayback())
++    if (IsGestureNeededForPlayback() || IsAutoplayBlocked())
+       return DOMExceptionCode::kNotAllowedError;
+   } else {
+     TryUnlockingUserGesture();
+@@ -318,6 +326,10 @@ bool AutoplayPolicy::IsGestureNeededForPlayback() const {
+   return !IsEligibleForAutoplayMuted();
+ }
+ 
++bool AutoplayPolicy::IsAutoplayBlocked() const {
++  return base::FeatureList::IsEnabled(features::kBlockMediaAutoplay);
++}
++
+ String AutoplayPolicy::GetPlayErrorMessage() const {
+   return IsUsingDocumentUserActivationRequiredPolicy()
+              ? kErrorAutoplayFuncUnified
+diff --git a/third_party/blink/renderer/core/html/media/autoplay_policy.h b/third_party/blink/renderer/core/html/media/autoplay_policy.h
+index ca5c996363ad8..2e0499d916eba 100644
+--- a/third_party/blink/renderer/core/html/media/autoplay_policy.h
++++ b/third_party/blink/renderer/core/html/media/autoplay_policy.h
+@@ -98,6 +98,8 @@ class CORE_EXPORT AutoplayPolicy final
+   // gesture is currently being processed.
+   bool IsGestureNeededForPlayback() const;
+ 
++  bool IsAutoplayBlocked() const;
++
+   // Returns an error string to be used by the HTMLMediaElement when the play()
+   // method fails because of autoplay restrictions.
+   String GetPlayErrorMessage() const;
+diff --git a/third_party/blink/renderer/core/html/media/html_media_element.cc b/third_party/blink/renderer/core/html/media/html_media_element.cc
+index bc96dc883958b..722bbcff8229a 100644
+--- a/third_party/blink/renderer/core/html/media/html_media_element.cc
++++ b/third_party/blink/renderer/core/html/media/html_media_element.cc
+@@ -2663,7 +2663,8 @@ String HTMLMediaElement::EffectivePreload() const {
+ }
+ 
+ WebMediaPlayer::Preload HTMLMediaElement::EffectivePreloadType() const {
+-  if (Autoplay() && !autoplay_policy_->IsGestureNeededForPlayback())
++  if (Autoplay() && !autoplay_policy_->IsGestureNeededForPlayback() &&
++      !autoplay_policy_->IsAutoplayBlocked())
+     return WebMediaPlayer::kPreloadAuto;
+ 
+   WebMediaPlayer::Preload preload = PreloadType();