Bug 1412195 - Track all changes to TabChild active state (r=bevis)

MozReview-Commit-ID: 7nQjquaM4sQ

docshell/base/nsDocShell.cpp

@@ -6335,6 +6335,10 @@ nsDocShell::SetIsActive(bool aIsActive)
   // Keep track ourselves.
   mIsActive = aIsActive;
 
+  if (TabChild* tc = TabChild::GetFrom(this)) {
+    tc->OnDocShellActivated(aIsActive);
+  }
+
   // Clear prerender flag if necessary.
   if (mIsPrerendered && aIsActive) {
     MOZ_ASSERT(mPrerenderGlobalHistory.get());