Tighten scope of activation changes made as part of Mac spaces restore.

There was multi-platform fallout from making activation less aggressive
in r701411 so that when a session is restored on Mac with windows in
multiple spaces, the system won't switch spaces as those windows are
created and activated.

This rolls back all of the cross-platform changes from r701411 and
r710397, replacing them with behind one tweak to skip activating windows
after restoring their tabs, currently guarded to macOS-only.

Bug: 1019048, 1018885
Change-Id: Id45d2029cf8a5f2af08e7ec3aba911ff2b664a10
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1910282Reviewed-by: Avi Drissman <avi@chromium.org>
Commit-Queue: Sidney San Martín <sdy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#714657}

chrome/browser/sessions/session_restore.cc

@@ -478,12 +478,8 @@ class SessionRestoreImpl : public BrowserListObserver {
     chromeos::BootTimesRecorder::Get()->AddLoginTimeMarker(
         "SessionRestore-CreatingTabs-End", false);
 #endif
-    if (browser_to_activate) {
-      // |browser_to_activate| may be minimized. Show it before activating it to
-      // avoid having a window with no content. https://crbug.com/1018885
-      browser_to_activate->window()->Show();
+    if (browser_to_activate)
       browser_to_activate->window()->Activate();
-    }
 
     // If last_normal_browser is NULL and urls_to_open_ is non-empty,
     // FinishedTabCreation will create a new TabbedBrowser and add the urls to
@@ -663,8 +659,7 @@ class SessionRestoreImpl : public BrowserListObserver {
     if (browser_ == browser)
       return;
 
-    if (!browser->window()->IsVisible() && !browser->window()->IsMinimized())
-      browser->window()->Show();
+    browser->window()->Show();
     browser->set_is_session_restore(false);
   }
 

chrome/browser/ui/browser_tabrestore.cc

@@ -7,6 +7,7 @@
 #include <memory>
 #include <utility>
 
+#include "build/build_config.h"
 #include "chrome/browser/extensions/tab_helper.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/browser/sessions/session_restore.h"
@@ -126,8 +127,16 @@ WebContents* AddRestoredTab(
   }
 
   if (select) {
-    if (!browser->window()->IsMinimized())
-      browser->window()->Show();
+    if (
+#if defined(OS_MACOSX)
+        // Activating a window on another space causes the system to switch to
+        // that space. Since the session restore process shows and activates
+        // windows itself, activating windows here should be safe to skip.
+        // Cautiously apply only to macOS, for now (https://crbug.com/1019048).
+        !from_session_restore &&
+#endif
+        !browser->window()->IsMinimized())
+      browser->window()->Activate();
   } else {
     // We set the size of the view here, before Blink does its initial layout.
     // If we don't, the initial layout of background tabs will be performed