Add setting to isolate zoom changes by default.

components/zoom/zoom_controller.h

Index: components/zoom/zoom_controller.h
diff --git a/components/zoom/zoom_controller.h b/components/zoom/zoom_controller.h
index 159b74843371ba3aec1c71f9b45468729e78162b..a7a18a3858d10f7114f8b272b4ffb0d7ac0129f8 100644
--- a/components/zoom/zoom_controller.h
+++ b/components/zoom/zoom_controller.h
@@ -8,6 +8,7 @@
 #include <memory>
 
 #include "base/compiler_specific.h"
+#include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/observer_list.h"
@@ -15,8 +16,11 @@
 #include "content/public/browser/host_zoom_map.h"
 #include "content/public/browser/web_contents_observer.h"
 #include "content/public/browser/web_contents_user_data.h"
+#include "content/public/browser/zoom_level_delegate.h"
 
 class ZoomControllerTest;
+FORWARD_DECLARE_TEST(ZoomControllerTest, OnDefaultZoomScopeChanged);
+FORWARD_DECLARE_TEST(ZoomControllerPerTabTest, OnDefaultZoomScopeChanged);
 
 namespace content {
 class WebContents;
@@ -48,6 +52,7 @@ class ZoomController : public content::WebContentsObserver,
     // Results in default zoom behavior, i.e. zoom changes are handled
     // automatically and on a per-origin basis, meaning that other tabs
     // navigated to the same origin will also zoom.
+    // TODO Would we want to rename this?

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

Nit: write as "TODO(<ldap>):"

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

Acknowledged.

     ZOOM_MODE_DEFAULT,
     // Results in zoom changes being handled automatically, but on a per-tab
     // basis. Tabs in this zoom mode will not be affected by zoom changes in
@@ -155,6 +160,11 @@ class ZoomController : public content::WebContentsObserver,
   void WebContentsDestroyed() override;
   void RenderFrameHostChanged(content::RenderFrameHost* old_host,
                               content::RenderFrameHost* new_host) override;
+  void DidCloneToNewWebContents(
+      content::WebContents* old_web_contents,
+      content::WebContents* new_web_contents) override;
+  void WebContentsReplaced(content::WebContents* old_web_contents,
+                           content::WebContents* new_web_contents) override;
 
  protected:
   // Protected for testing.
@@ -163,9 +173,16 @@ class ZoomController : public content::WebContentsObserver,
  private:
   friend class content::WebContentsUserData<ZoomController>;
   friend class ::ZoomControllerTest;
+  FRIEND_TEST_ALL_PREFIXES(::ZoomControllerTest, OnDefaultZoomScopeChanged);
+  FRIEND_TEST_ALL_PREFIXES(::ZoomControllerPerTabTest,
+                           OnDefaultZoomScopeChanged);
 
   void ResetZoomModeOnNavigationIfNeeded(const GURL& url);
+  void UpdateZoomModeOnScopeChangeIfNeeded();
+  void PreserveTemporaryZoomLevel(content::WebContents* old_web_contents,
+                                  content::WebContents* new_web_contents) const;
   void OnZoomLevelChanged(const content::HostZoomMap::ZoomLevelChange& change);
+  void OnDefaultZoomScopeChanged();
 
   // Updates the zoom icon and zoom percentage based on current values and
   // notifies the observer if changes have occurred. |host| may be empty,
@@ -179,6 +196,10 @@ class ZoomController : public content::WebContentsObserver,
   // The current zoom mode.
   ZoomMode zoom_mode_;
 
+  // Whether zoom changes are by default scoped to a page's origin.
+  // If false, they are scoped to the tab.
+  bool default_per_origin_;
+
   // Current zoom level.
   double zoom_level_;
 
@@ -196,6 +217,8 @@ class ZoomController : public content::WebContentsObserver,
   content::HostZoomMap* host_zoom_map_;
 
   std::unique_ptr<content::HostZoomMap::Subscription> zoom_subscription_;
+  std::unique_ptr<content::ZoomLevelDelegate::DefaultZoomScopeSubscription>
+      default_zoom_scope_subscription_;
 
   DISALLOW_COPY_AND_ASSIGN(ZoomController);
 };