New tabCapture.captureOffscreenTab API, initially for Presentation API 1UA mode

chrome/browser/extensions/api/tab_capture/offscreen_presentation.cc

Index: chrome/browser/extensions/api/tab_capture/offscreen_presentation.cc
diff --git a/chrome/browser/extensions/api/tab_capture/offscreen_presentation.cc b/chrome/browser/extensions/api/tab_capture/offscreen_presentation.cc
index 2ccd614b8035321582aac9c7c12777da22d06bdf..ebd4c6be281b57621c7590c7e1a47ea39c63475e 100644
--- a/chrome/browser/extensions/api/tab_capture/offscreen_presentation.cc
+++ b/chrome/browser/extensions/api/tab_capture/offscreen_presentation.cc
@@ -381,14 +381,12 @@ void OffscreenPresentation::RequestMediaAccessPermission(
   // WebContents.
   content::BrowserContext* const extension_browser_context =
       owner_->extension_web_contents()->GetBrowserContext();
-  std::string extension_id;
-  for (const ExtensionHost* host :
-           ProcessManager::Get(extension_browser_context)->background_hosts()) {
-    if (host->host_contents() == owner_->extension_web_contents()) {
-      extension_id = host->extension_id();
-      break;
-    }
-  }
+  const extensions::Extension* const extension =
+      ProcessManager::Get(extension_browser_context)->
+          GetExtensionForWebContents(owner_->extension_web_contents());
+  const std::string extension_id = extension ? extension->id() : "";
+  LOG_IF(DFATAL, extension_id.empty())
+      << "Extension that started this OffscreenPresentation was not found.";
 
   // If verified, allow any tab capture audio/video devices that were requested.
   extensions::TabCaptureRegistry* const tab_capture_registry =