Bug 1397426 - Rename TabChild's notion of "active tabs" to "visible tabs" and move logic into renderLayers. r=billm

MozReview-Commit-ID: 1bBNwew7uCk

docshell/base/nsDocShell.cpp

@@ -5824,10 +5824,6 @@ 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());