Bug 1594794 - NULL Crash in MediaKeySystemAccessManager::CheckDoesWindowSupportProtectedMedia r=bryce,bzbarsky

This change fixes a crash when there is no BrowserChild available (i.e., e10s is is turned off in Windows). In this case, the window is assumed to support protected media and will proceed without making the IPC call to check.

Differential Revision: https://phabricator.services.mozilla.com/D52190

--HG--
extra : moz-landing-system : lando

Author: thomasmo

dom/media/eme/MediaKeySystemAccessManager.cpp

@@ -132,6 +132,16 @@ void MediaKeySystemAccessManager::CheckDoesWindowSupportProtectedMedia(
   // On other platforms windows should always support protected media.
 #ifdef XP_WIN
   RefPtr<BrowserChild> browser(BrowserChild::GetFrom(mWindow));
+  if (!browser) {
+    if (!XRE_IsParentProcess() || XRE_IsE10sParentProcess()) {
+      MOZ_CRASH("BrowserChild should only be unavailable with e10s off");
+    }
+
+    MKSAM_LOG_DEBUG("Allowing protected media on Windows with e10s off.");
+
+    OnDoesWindowSupportProtectedMedia(true, std::move(aRequest));
+    return;
+  }
 
   RefPtr<MediaKeySystemAccessManager> self(this);
 
@@ -156,6 +166,7 @@ void MediaKeySystemAccessManager::CheckDoesWindowSupportProtectedMedia(
           self->OnDoesWindowSupportProtectedMedia(false, std::move(request));
         }
       });
+
 #else
   // Non-Windows OS windows always support protected media.
   MKSAM_LOG_DEBUG(