Ensure keep alive count gets incremented on tts engine load

Adds back call mistakenly removed in
https://chromium-review.googlesource.com/c/chromium/src/+/2496287

R=dmazzoni@chromium.org

Change-Id: I3fab6b94a8c9c80527b0b2d451ef1d6911be1f10
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2532928Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#826388}

chrome/browser/speech/extension_api/tts_engine_extension_observer_chromeos.cc

@@ -200,6 +200,9 @@ void TtsEngineExtensionObserverChromeOS::OnExtensionLoaded(
   if (extension->permissions_data()->HasAPIPermission(
           extensions::APIPermission::kTtsEngine)) {
     engine_extension_ids_.insert(extension->id());
+
+    if (extension->id() == extension_misc::kGoogleSpeechSynthesisExtensionId)
+      UpdateGoogleSpeechSynthesisKeepAliveCountOnReload(browser_context);
   }
 }