Fix some grammar in tab_strip_model.cc

chrome/browser/tabs/tab_strip_model.cc

Index: chrome/browser/tabs/tab_strip_model.cc
diff --git a/chrome/browser/tabs/tab_strip_model.cc b/chrome/browser/tabs/tab_strip_model.cc
index beeb23269be27dd96843cfe572243bfd404957ba..8ece105621bb67851132da4aec44efb4d90088a1 100644
--- a/chrome/browser/tabs/tab_strip_model.cc
+++ b/chrome/browser/tabs/tab_strip_model.cc
@@ -562,7 +562,7 @@ void TabStripModel::SetTabPinned(int index, bool pinned) {
       NOTREACHED();
       return;
     }
-    // Changing the pinned state of an app tab doesn't effect it's mini-tab
+    // Changing the pinned state of an app tab doesn't affect its mini-tab
     // status.
     contents_data_[index]->pinned = pinned;
   } else {