Fix the remaining cases of classes implementing non-existent TabContentsDelegate::IsPopup().

chrome/browser/sidebar/sidebar_container.cc

Index: chrome/browser/sidebar/sidebar_container.cc
diff --git a/chrome/browser/sidebar/sidebar_container.cc b/chrome/browser/sidebar/sidebar_container.cc
index f219d65818a4fc4a05e12f595b4da0b4dee203a7..d428971e3c6c0289b7fc92f56ad2e9afa35f4d08 100644
--- a/chrome/browser/sidebar/sidebar_container.cc
+++ b/chrome/browser/sidebar/sidebar_container.cc
@@ -106,10 +106,6 @@ void SidebarContainer::SetTitle(const string16& title) {
   title_ = title;
 }
 
-bool SidebarContainer::IsPopup(const TabContents* source) const {
-  return false;
-}
-
 content::JavaScriptDialogCreator*
 SidebarContainer::GetJavaScriptDialogCreator() {
   return GetJavaScriptDialogCreatorInstance();