Add setting to isolate zoom changes by default.

chrome/browser/ui/tabs/tab_strip_model.cc

Index: chrome/browser/ui/tabs/tab_strip_model.cc
diff --git a/chrome/browser/ui/tabs/tab_strip_model.cc b/chrome/browser/ui/tabs/tab_strip_model.cc
index 737b80928761843e6208a44f179f180653d14358..1aebba7279140ab69321f1c0de7171a0d479c481 100644
--- a/chrome/browser/ui/tabs/tab_strip_model.cc
+++ b/chrome/browser/ui/tabs/tab_strip_model.cc
@@ -25,6 +25,7 @@
 #include "chrome/browser/ui/web_contents_sizer.h"
 #include "chrome/common/url_constants.h"
 #include "components/web_modal/web_contents_modal_dialog_manager.h"
+#include "components/zoom/zoom_controller.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/user_metrics.h"
 #include "content/public/browser/web_contents.h"
@@ -342,6 +343,13 @@ WebContents* TabStripModel::ReplaceWebContentsAt(int index,
 
   contents_data_[index]->SetWebContents(new_contents);
 
+  // Notify the ZoomController of the replacement of its WebContents so that it
+  // may clone any per-tab zoom information.
+  zoom::ZoomController* zoom_controller =
+      zoom::ZoomController::FromWebContents(old_contents);
+  if (zoom_controller)
+    zoom_controller->WebContentsReplaced(new_contents);
+
   for (auto& observer : observers_)
     observer.TabReplacedAt(this, old_contents, new_contents, index);