Add sidebar views implementation using ExtensionSystem SidebarManager

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 4f2867eb0c601463d3e2af99be08b693005ad2af..72a079dbf0b6a1d8f141e235841efedbf7bc1a84 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1469,6 +1469,8 @@ const char kDisablePluginFinder[] = "plugins.disable_plugin_finder";
 // Customized app page names that appear on the New Tab Page.
 const char kNtpAppPageNames[] = "ntp.app_page_names";
 
+const char kExtensionSidebarWidth[] = "extensions.sidebar.width";
+
 #if defined(OS_ANDROID)
 // Keeps track of currently open tabs collapsed state in the Other Devices menu.
 const char kNtpCollapsedCurrentlyOpenTabs[] = "ntp.collapsed_open_tabs";