[ios] Extend BrowserList API.

ios/shared/chrome/browser/ui/browser_list/browser_list.h

Index: ios/shared/chrome/browser/ui/browser_list/browser_list.h
diff --git a/ios/shared/chrome/browser/ui/browser_list/browser_list.h b/ios/shared/chrome/browser/ui/browser_list/browser_list.h
index 6f4446d93134276b5307c4ac13e53cd73ad5e798..8cb960aeee4c7bb7d8b23eca7862c18292fc43b8 100644
--- a/ios/shared/chrome/browser/ui/browser_list/browser_list.h
+++ b/ios/shared/chrome/browser/ui/browser_list/browser_list.h
@@ -24,8 +24,8 @@ class BrowserList : public base::SupportsUserData::Data {
 
   static BrowserList* FromBrowserState(ios::ChromeBrowserState* browser_state);
 
-  // Returns the number of open Browsers.
-  int GetBrowserCount() const;
+  // Returns the number of Browsers in the BrowserList.
+  int count() const { return static_cast<int>(browsers_.size()); }
 
   // Returns whether the specified index is valid.
   int ContainsIndex(int index) const;
@@ -33,12 +33,18 @@ class BrowserList : public base::SupportsUserData::Data {
   // Returns the Browser at the specified index.
   Browser* GetBrowserAtIndex(int index) const;
 
+  // Returns the index of the specified Browser, or kInvalidIndex if not found.
+  int GetIndexOfBrowser(const Browser* browser) const;
+
   // Creates and returns a new Browser instance.
   Browser* CreateNewBrowser();
 
   // Closes the Browser at the specified index.
   void CloseBrowserAtIndex(int index);
 
+  // Invalid index.
+  static const int kInvalidIndex = -1;
+
  private:
   ios::ChromeBrowserState* browser_state_;
   std::vector<std::unique_ptr<Browser>> browsers_;