Bug 1572798 - Make content browsing contexts for tabs start as inactive. r=nika

Otherwise autoplay blocking until-in-foreground breaks with the other
patch in this bug, because it unblocks media playback once a browsing
context is active for the first time.

Differential Revision: https://phabricator.services.mozilla.com/D42329

browser/base/content/tabbrowser.js

@@ -1970,6 +1970,7 @@
       uriIsAboutBlank,
       userContextId,
       skipLoad,
+      initiallyActive,
     } = {}) {
       let b = document.createXULElement("browser");
       // Use the JSM global to create the permanentKey, so that if the
@@ -2002,6 +2003,10 @@
         b.setAttribute(attribute, defaultBrowserAttributes[attribute]);
       }
 
+      if (!initiallyActive) {
+        b.setAttribute("initiallyactive", "false");
+      }
+
       if (userContextId) {
         b.setAttribute("usercontextid", userContextId);
       }

docshell/base/BrowsingContext.cpp

@@ -344,8 +344,19 @@ already_AddRefed<BrowsingContext> BrowsingContext::CreateDetached(
   }
 
   nsContentUtils::GenerateUUIDInPlace(fields.mHistoryID);
-  fields.mExplicitActive =
-      parentBC ? ExplicitActiveStatus::None : ExplicitActiveStatus::Active;
+  fields.mExplicitActive = [&] {
+    if (parentBC) {
+      // Non-root browsing-contexts inherit their status from its parent.
+      return ExplicitActiveStatus::None;
+    }
+    if (aType == Type::Content) {
+      // Content gets managed by the chrome front-end / embedder element and
+      // starts as inactive.
+      return ExplicitActiveStatus::Inactive;
+    }
+    // Chrome starts as active.
+    return ExplicitActiveStatus::Active;
+  }();
 
   fields.mFullZoom = parentBC ? parentBC->FullZoom() : 1.0f;
   fields.mTextZoom = parentBC ? parentBC->TextZoom() : 1.0f;
@@ -576,6 +587,14 @@ bool BrowsingContext::IsActive() const {
   return false;
 }
 
+void BrowsingContext::SetInitiallyActive() {
+  MOZ_DIAGNOSTIC_ASSERT(!EverAttached());
+  MOZ_DIAGNOSTIC_ASSERT(IsContent());
+  MOZ_DIAGNOSTIC_ASSERT(IsTop());
+
+  mFields.SetWithoutSyncing<IDX_ExplicitActive>(ExplicitActiveStatus::Active);
+}
+
 bool BrowsingContext::GetIsActiveBrowserWindow() {
   if (!XRE_IsParentProcess()) {
     return Top()->GetIsActiveBrowserWindowInternal();
@@ -633,8 +652,7 @@ void BrowsingContext::SetEmbedderElement(Element* aEmbedder) {
     if (XRE_IsParentProcess() && IsTopContent()) {
       nsAutoString messageManagerGroup;
       if (aEmbedder->IsXULElement()) {
-        aEmbedder->GetAttr(kNameSpaceID_None, nsGkAtoms::messagemanagergroup,
-                           messageManagerGroup);
+        aEmbedder->GetAttr(nsGkAtoms::messagemanagergroup, messageManagerGroup);
       }
       txn.SetMessageManagerGroup(messageManagerGroup);
 

docshell/base/BrowsingContext.h

@@ -498,6 +498,8 @@ class BrowsingContext : public nsILoadContext, public nsWrapperCache {
                       aRv);
   }
 
+  void SetInitiallyActive();
+
   bool AuthorStyleDisabledDefault() const {
     return GetAuthorStyleDisabledDefault();
   }

dom/base/nsFrameLoader.cpp

@@ -3745,14 +3745,16 @@ bool nsFrameLoader::EnsureBrowsingContextAttached() {
 
   // Inherit the `use` flags from our parent BrowsingContext.
   bool usePrivateBrowsing = parentContext->UsePrivateBrowsing();
-  bool useRemoteSubframes = parentContext->UseRemoteSubframes();
-  bool useRemoteTabs = parentContext->UseRemoteTabs();
+  const bool useRemoteSubframes = parentContext->UseRemoteSubframes();
+  const bool useRemoteTabs = parentContext->UseRemoteTabs();
+
+  const bool isContent = mPendingBrowsingContext->IsContent();
 
   // Determine the exact OriginAttributes which should be used for our
   // BrowsingContext. This will be used to initialize OriginAttributes if the
   // BrowsingContext has not already been created.
   OriginAttributes attrs;
-  if (mPendingBrowsingContext->IsContent()) {
+  if (isContent) {
     if (mPendingBrowsingContext->GetParent()) {
       MOZ_ASSERT(mPendingBrowsingContext->GetParent() == parentContext);
       parentContext->GetOriginAttributes(attrs);
@@ -3784,8 +3786,7 @@ bool nsFrameLoader::EnsureBrowsingContextAttached() {
     // <iframe mozbrowser> is allowed to set `mozprivatebrowsing` to
     // force-enable private browsing.
     if (OwnerIsMozBrowserFrame()) {
-      if (mOwnerContent->HasAttr(kNameSpaceID_None,
-                                 nsGkAtoms::mozprivatebrowsing)) {
+      if (mOwnerContent->HasAttr(nsGkAtoms::mozprivatebrowsing)) {
         attrs.SyncAttributesWithPrivateBrowsing(true);
         usePrivateBrowsing = true;
       }
@@ -3815,6 +3816,14 @@ bool nsFrameLoader::EnsureBrowsingContextAttached() {
   rv = mPendingBrowsingContext->SetRemoteSubframes(useRemoteSubframes);
   NS_ENSURE_SUCCESS(rv, false);
 
+  if (isContent && mOwnerContent->IsXULElement() &&
+      !mOwnerContent->AttrValueIs(kNameSpaceID_None, nsGkAtoms::initiallyactive,
+                                  nsGkAtoms::_false, eIgnoreCase)) {
+    // Content <browser> elements are active, unless told otherwise by the
+    // initiallyactive attribute.
+    mPendingBrowsingContext->SetInitiallyActive();
+  }
+
   // Finish attaching.
   mPendingBrowsingContext->EnsureAttached();
   return true;

toolkit/components/printing/content/printUtils.js

@@ -156,6 +156,7 @@ var PrintUtils = {
         userContextId: browsingContext.originAttributes.userContextId,
         initialBrowsingContextGroupId: browsingContext.group.id,
         skipLoad: true,
+        initiallyActive: true,
       });
       browser.addEventListener("DOMWindowClose", function(e) {
         // Ignore close events from printing, see the code creating browsers in

xpcom/ds/StaticAtoms.py

@@ -2217,6 +2217,7 @@ STATIC_ATOMS = [
     Atom("forcemessagemanager", "forcemessagemanager"),
     Atom("preloadedState", "preloadedState"),
     Atom("initialBrowsingContextGroupId", "initialBrowsingContextGroupId"),
+    Atom("initiallyactive", "initiallyactive"),
     # windows media query names
     Atom("windows_win7", "windows-win7"),
     Atom("windows_win8", "windows-win8"),