Add setting to isolate zoom changes by default.

chrome/common/pref_names.cc

Index: chrome/common/pref_names.cc
diff --git a/chrome/common/pref_names.cc b/chrome/common/pref_names.cc
index 7b14c9a6ea83e6f322a32cfadd4009a4f8552076..e075ff5b4c02ae5e1aa094634445c26c4be134a1 100644
--- a/chrome/common/pref_names.cc
+++ b/chrome/common/pref_names.cc
@@ -1097,6 +1097,11 @@ const char kPartitionDefaultZoomLevel[] = "partition.default_zoom_level";
 // be displayed at the default zoom level.
 const char kPartitionPerHostZoomLevels[] = "partition.per_host_zoom_levels";
 
+// Whether zoom changes should be scoped to origins by default.
+// If false, zoom changes are per-tab.
+const char kPartitionZoomScopeIsPerOrigin[] =

[Kevin McNee, 2017/02/03 23:17:20]

Shall we get UMA data about the usage of this option?

[wjmaclean, 2017/02/06 16:09:07]

Definitely!

+    "partition.zoom_scope_is_per_origin";
+
 #if !defined(OS_ANDROID)
 const char kPinnedTabs[] = "pinned_tabs";
 #endif