[Session restore] Expose lazy mode and fix browser tests.

chrome/browser/sessions/better_session_restore_browsertest.cc

Index: chrome/browser/sessions/better_session_restore_browsertest.cc
diff --git a/chrome/browser/sessions/better_session_restore_browsertest.cc b/chrome/browser/sessions/better_session_restore_browsertest.cc
index b6c902602705912c394a4dfe3bd2a2f7ec7deb59..2a2546aa5e844b532d6eb953f38913970e1331d7 100644
--- a/chrome/browser/sessions/better_session_restore_browsertest.cc
+++ b/chrome/browser/sessions/better_session_restore_browsertest.cc
@@ -214,6 +214,14 @@ class BetterSessionRestoreTest : public InProcessBrowserTest {
   }
 
   void CheckReloadedPageNotRestored() {
+    // If only active tabs are loaded, force loading of the tabs.
+    if (SessionRestore::WillLoadActiveTabsOnly()) {
+      for (int i = 0; i < browser()->tab_strip_model()->count(); i++) {
+        content::WebContents* web_contents =
+            browser()->tab_strip_model()->GetWebContentsAt(i);
+        web_contents->GetController().LoadIfNecessary();
+      }
+    }
     CheckReloadedPageNotRestored(browser());
   }