Add tabs.onReplaced event to notify listeners of tabs being swapped due to prerendering or instant.

chrome/browser/extensions/browser_event_router.cc

Index: chrome/browser/extensions/browser_event_router.cc
diff --git a/chrome/browser/extensions/browser_event_router.cc b/chrome/browser/extensions/browser_event_router.cc
index bf457f9fb319c29063e9f8e87ba6efa479c9df12..b351baba20a7456f2d4621132b8740d25c328441 100644
--- a/chrome/browser/extensions/browser_event_router.cc
+++ b/chrome/browser/extensions/browser_event_router.cc
@@ -471,6 +471,19 @@ void BrowserEventRouter::TabReplacedAt(TabStripModel* tab_strip_model,
                                        WebContents* old_contents,
                                        WebContents* new_contents,
                                        int index) {
+  // Notify listeners that the next tabs closing or being added are due to
+  // WebContents being swapped.
+  scoped_ptr<ListValue> args(new ListValue());
+  args->Append(Value::CreateIntegerValue(
+      ExtensionTabUtil::GetTabId(new_contents)));
+  args->Append(Value::CreateIntegerValue(
+      ExtensionTabUtil::GetTabId(old_contents)));
+
+  DispatchEvent(Profile::FromBrowserContext(new_contents->GetBrowserContext()),
+                events::kOnTabSwapped,
+                args.Pass(),
+                EventRouter::USER_GESTURE_UNKNOWN);
+
   TabClosingAt(tab_strip_model, old_contents, index);
   TabInsertedAt(new_contents, index, tab_strip_model->active_index() == index);

[Matt Perry, 2012/12/18 18:04:02]

Can we remove these two calls? The downside is that extensions may have been
depending on them before, but maybe they were broken anyway.

[justinlin, 2012/12/19 23:42:42]

Yea, I thought about removing at first, but wanted to avoid breaking
functionality. The docs do say that removed events are fired when a tab is
closed, so you're probably right that it was broken and would fire when the tab
wasn't actually closed but replaced instead. Removed.

 }