Force guest profiles to return default startup prefs.

chrome/browser/sessions/session_restore.cc

Index: chrome/browser/sessions/session_restore.cc
diff --git a/chrome/browser/sessions/session_restore.cc b/chrome/browser/sessions/session_restore.cc
index 49b446873dcf51153daf3469ba46dd8e84370b6c..be9816dea967feb064c9769c1cb79ed777741728 100644
--- a/chrome/browser/sessions/session_restore.cc
+++ b/chrome/browser/sessions/session_restore.cc
@@ -86,6 +86,12 @@ bool HasSingleNewTabPage(Browser* browser) {
          search::IsInstantNTP(active_tab);
 }
 
+Profile* SafeProfileForNewWindows(Profile* profile) {
+  // Guest sessions must always be OffTheRecord when opening windows.
+  return profile->IsGuestSession() ? profile->GetOffTheRecordProfile()

[sky, 2017/06/07 19:21:40]

I'm a little confused by this, and forgive me because I couldn't readily find
docs for guest mode. It's my understanding that when you exit guest mode we
throw everything away. If that's the case, why and how are we triggering session
restore of a guest session? Shouldn't all the data be temporary? If it's because
of a crash and parts of the guest session were left around, shouldn't we clean
them up and not attempt a restore?

[shrike, 2017/06/07 20:19:05]

Gosh, I wish could even start to comment. I know nothing about all this stuff,
but was mirroring a similar change I made in
https://codereview.chromium.org/2899313005 to fix a different set of crashers.

The following crash seems to show that somehow the condition I'm trying to guard
against can happen (which it sounds like you're saying should not happen):

https://crash.corp.google.com/browse?q=product.name%3D%27Chrome_Mac%27%20AND%...

+                                   : profile;
+}
+
 class SessionRestoreImpl;
 
 // Pointers to SessionRestoreImpls which are currently restoring the session.
@@ -214,7 +220,8 @@ class SessionRestoreImpl : public content::NotificationObserver {
     bool use_new_window = disposition == WindowOpenDisposition::NEW_WINDOW;
 
     Browser* browser = use_new_window
-                           ? new Browser(Browser::CreateParams(profile_, true))
+                           ? new Browser(Browser::CreateParams(
+                                 SafeProfileForNewWindows(profile_), true))
                            : browser_;
 
     RecordAppLaunchForTab(browser, tab, selected_index);
@@ -292,7 +299,8 @@ class SessionRestoreImpl : public content::NotificationObserver {
                                std::vector<RestoredTab>* contents_created) {
     Browser* browser = nullptr;
     if (!created_tabbed_browser && always_create_tabbed_browser_) {
-      browser = new Browser(Browser::CreateParams(profile_, false));
+      browser = new Browser(
+          Browser::CreateParams(SafeProfileForNewWindows(profile_), false));
       if (urls_to_open_.empty()) {
         // No tab browsers were created and no URLs were supplied on the command
         // line. Open the new tab page.
@@ -629,11 +637,12 @@ class SessionRestoreImpl : public content::NotificationObserver {
                                  const std::string& workspace,
                                  ui::WindowShowState show_state,
                                  const std::string& app_name) {
-    Browser::CreateParams params(type, profile_, false);
+    Profile* profile = SafeProfileForNewWindows(profile_);
+    Browser::CreateParams params(type, profile, false);
     if (!app_name.empty()) {
       const bool trusted_source = true;  // We only store trusted app windows.
       params = Browser::CreateParams::CreateForApp(app_name, trusted_source,
-                                                   bounds, profile_, false);
+                                                   bounds, profile, false);
     } else {
       params.initial_bounds = bounds;
     }