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..d7a2ee8337084671d3df661575fb9308af049927 100644
--- a/chrome/browser/ui/tabs/tab_strip_model.cc
+++ b/chrome/browser/ui/tabs/tab_strip_model.cc
@@ -342,6 +342,8 @@ WebContents* TabStripModel::ReplaceWebContentsAt(int index,
 
   contents_data_[index]->SetWebContents(new_contents);
 
+  old_contents->OnReplaced(new_contents);

[wjmaclean, 2017/01/19 21:09:05]

Can we perhaps re-name this to something like CloneZoomSettings()? Or have the
tab-strip do the cloning (if it can see the zoom controller, it could contact it
directly?)?

[Kevin McNee, 2017/01/25 23:42:56]

Done.

The zoom controller is now notified directly.

+
   for (auto& observer : observers_)
     observer.TabReplacedAt(this, old_contents, new_contents, index);