Showing previews UI for Offline Previews

chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java

Index: chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java b/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
index b3912fc66c46162eb4bb6691f54fea3376809637..aca92e50424c888b2e88723f1b267aeb4cc54c95 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/offlinepages/OfflinePageBridge.java
@@ -396,20 +396,28 @@ public class OfflinePageBridge {
 
     /**
      * Retrieves the extra request header to reload the offline page.
      * @param webContents Contents of the page to reload.
      * @return The extra request header string.
      */
     public String getOfflinePageHeaderForReload(WebContents webContents) {
         return nativeGetOfflinePageHeaderForReload(mNativeOfflinePageBridge, webContents);
     }
 
+    /**
+     * @return True if an offline preview is being shown.
+     * @param webContents Contents of the page to check.
+     */
+    public boolean isShowingOfflinePreview(WebContents webContents) {
+        return nativeIsShowingOfflinePreview(mNativeOfflinePageBridge, webContents);
+    }
+
     private static class CheckPagesExistOfflineCallbackInternal {
         private Callback<Set<String>> mCallback;
 
         CheckPagesExistOfflineCallbackInternal(Callback<Set<String>> callback) {
             mCallback = callback;
         }
 
         @CalledByNative("CheckPagesExistOfflineCallbackInternal")
         public void onResult(String[] results) {
             Set<String> resultSet = new HashSet<>();
@@ -522,11 +530,13 @@ public class OfflinePageBridge {
             String[] ids, Callback<Integer> callback);
     private native void nativeSelectPageForOnlineUrl(
             long nativeOfflinePageBridge, String onlineUrl, int tabId,
             Callback<OfflinePageItem> callback);
     private native void nativeSavePage(long nativeOfflinePageBridge, SavePageCallback callback,
             WebContents webContents, String clientNamespace, String clientId);
     private native void nativeSavePageLater(long nativeOfflinePageBridge, String url,
             String clientNamespace, String clientId, boolean userRequested);
     private native String nativeGetOfflinePageHeaderForReload(
             long nativeOfflinePageBridge, WebContents webContents);
+    private native boolean nativeIsShowingOfflinePreview(
+            long nativeOfflinePageBridge, WebContents webContents);
 }