[Offline pages] Filter out pages cached by different tabs on tab helper

chrome/browser/android/offline_pages/offline_page_utils.h

Index: chrome/browser/android/offline_pages/offline_page_utils.h
diff --git a/chrome/browser/android/offline_pages/offline_page_utils.h b/chrome/browser/android/offline_pages/offline_page_utils.h
index a09715d8c30c93e8b3418149745d13ef04e32095..8442472e41de8b0a5910dbf633b5dda007757eae 100644
--- a/chrome/browser/android/offline_pages/offline_page_utils.h
+++ b/chrome/browser/android/offline_pages/offline_page_utils.h
@@ -60,6 +60,11 @@ class OfflinePageUtils {
   // navigation, so it is unsafe to store a copy of the returned pointer.
   static const OfflinePageItem* GetOfflinePageFromWebContents(
       content::WebContents* web_contents);
+
+  // Gets an Android Tab ID from a tab containing |web_contents|. Returns false,
+  // when tab is not available. Returns true otherwise and sets |tab_id| to the
+  // ID of the tab.
+  static bool GetTabId(content::WebContents* web_contents, int* tab_id);
 };
 
 }  // namespace offline_pages