Extension: remove USER_GESTURE_ENABLED state from tab-change events.

A past fix for activation propagation from an extension button to
extension script seems to have added additional user activation
propagation path from tab-strip to all installed extensions:
https://chromiumcodereview.appspot.com/10821120/

This crack caused every tab-switching to activate /all/ installed
extensions, which seems bad.  Because of this, we encountered a security
issue with unintended top frame navigation from an iframe.  (Luckily
only tab switching was affected, not tab clicking.)

A user interaction with the tab-strip is different from an interaction
with extension buttons.  Tab-strip interactions are similar to those
on any browser-provided UI element like top menu: they don't at all
indicate the user's intention to interact with any extension or website.
Therefore, like clicks on top-menu and unlike clicks on extension
buttons, tab-switching should suppress activating any background script
thus prevent access to use user-activation gated APIs like popup,
fullscreen, navigation, etc.

Bug: 957633, 1035315
Change-Id: I8d56e02a3a2966521b7bbc4f4efadf67e1acc371
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2072654Reviewed-by: Devlin <rdevlin.cronin@chromium.org>
Commit-Queue: Mustaq Ahmed <mustaq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744802}

chrome/browser/extensions/api/tabs/tabs_event_router.cc

@@ -233,7 +233,7 @@ void TabsEventRouter::OnTabStripModelChanged(
 
   if (selection.active_tab_changed()) {
     DispatchActiveTabChanged(selection.old_contents, selection.new_contents,
-                             selection.new_model.active(), selection.reason);
+                             selection.new_model.active());
   }
 
   if (selection.selection_changed()) {
@@ -398,8 +398,7 @@ void TabsEventRouter::DispatchTabDetachedAt(WebContents* contents,
 
 void TabsEventRouter::DispatchActiveTabChanged(WebContents* old_contents,
                                                WebContents* new_contents,
-                                               int index,
-                                               int reason) {
+                                               int index) {
   auto args = std::make_unique<base::ListValue>();
   int tab_id = ExtensionTabUtil::GetTabId(new_contents);
   args->AppendInteger(tab_id);
@@ -414,24 +413,21 @@ void TabsEventRouter::DispatchActiveTabChanged(WebContents* old_contents,
   // deprecated events take two arguments: tabId, {windowId}.
   Profile* profile =
       Profile::FromBrowserContext(new_contents->GetBrowserContext());
-  EventRouter::UserGestureState gesture =
-      reason & CHANGE_REASON_USER_GESTURE
-      ? EventRouter::USER_GESTURE_ENABLED
-      : EventRouter::USER_GESTURE_NOT_ENABLED;
+
   DispatchEvent(profile, events::TABS_ON_SELECTION_CHANGED,
                 api::tabs::OnSelectionChanged::kEventName,
-                args->CreateDeepCopy(), gesture);
+                args->CreateDeepCopy(), EventRouter::USER_GESTURE_UNKNOWN);
   DispatchEvent(profile, events::TABS_ON_ACTIVE_CHANGED,
                 api::tabs::OnActiveChanged::kEventName, std::move(args),
-                gesture);
+                EventRouter::USER_GESTURE_UNKNOWN);
 
   // The onActivated event takes one argument: {windowId, tabId}.
   auto on_activated_args = std::make_unique<base::ListValue>();
   object_args->Set(tabs_constants::kTabIdKey, std::make_unique<Value>(tab_id));
   on_activated_args->Append(std::move(object_args));
-  DispatchEvent(profile, events::TABS_ON_ACTIVATED,
-                api::tabs::OnActivated::kEventName,
-                std::move(on_activated_args), gesture);
+  DispatchEvent(
+      profile, events::TABS_ON_ACTIVATED, api::tabs::OnActivated::kEventName,
+      std::move(on_activated_args), EventRouter::USER_GESTURE_UNKNOWN);
 }
 
 void TabsEventRouter::DispatchTabSelectionChanged(

chrome/browser/extensions/api/tabs/tabs_event_router.h

@@ -95,8 +95,7 @@ class TabsEventRouter : public TabStripModelObserver,
                              bool was_active);
   void DispatchActiveTabChanged(content::WebContents* old_contents,
                                 content::WebContents* new_contents,
-                                int index,
-                                int reason);
+                                int index);
   void DispatchTabSelectionChanged(TabStripModel* tab_strip_model,
                                    const ui::ListSelectionModel& old_model);
   void DispatchTabMoved(content::WebContents* contents,