Enable download page action for error page

chrome/android/java/src/org/chromium/chrome/browser/download/DownloadUtils.java

Index: chrome/android/java/src/org/chromium/chrome/browser/download/DownloadUtils.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadUtils.java b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadUtils.java
index 663a775e1b430e9285c0b257232a78b2bbdaaa4c..f9fd95bea9d7f1c3900db42fc1309f30efb420dc 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadUtils.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadUtils.java
@@ -38,6 +38,8 @@ import org.chromium.chrome.browser.download.ui.BackendProvider;
 import org.chromium.chrome.browser.download.ui.BackendProvider.DownloadDelegate;
 import org.chromium.chrome.browser.download.ui.DownloadFilter;
 import org.chromium.chrome.browser.download.ui.DownloadHistoryItemWrapper;
+import org.chromium.chrome.browser.offlinepages.ClientId;
+import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
 import org.chromium.chrome.browser.offlinepages.downloads.OfflinePageDownloadBridge;
 import org.chromium.chrome.browser.tab.Tab;
 import org.chromium.chrome.browser.tabmodel.TabModel.TabLaunchType;
@@ -187,10 +189,21 @@ public class DownloadUtils {
      * @param context Context to pull resources from.
      */
     public static void downloadOfflinePage(Context context, Tab tab) {
-        final OfflinePageDownloadBridge bridge = new OfflinePageDownloadBridge(tab.getProfile());
-        bridge.startDownload(tab);
-        bridge.destroy();
-        DownloadUtils.recordDownloadPageMetrics(tab);
+        if (tab.isShowingErrorPage()) {
+            // The download needs to be scheduled to happen at later time due to current network
+            // error.
+            ClientId clientId = ClientId.createGuidClientIdForNamespace(
+                    OfflinePageBridge.ASYNC_NAMESPACE);
+            final OfflinePageBridge bridge = OfflinePageBridge.getForProfile(tab.getProfile());
+            bridge.savePageLater(tab.getUrl(), clientId, true /* userRequested */);
+        } else {
+            // Otherwise, the download can be started immediately.
+            final OfflinePageDownloadBridge bridge =
+                    new OfflinePageDownloadBridge(tab.getProfile());
+            bridge.startDownload(tab);
+            bridge.destroy();
+            DownloadUtils.recordDownloadPageMetrics(tab);
+        }
     }
 
     /**
@@ -201,13 +214,17 @@ public class DownloadUtils {
     public static boolean isAllowedToDownloadPage(Tab tab) {
         if (tab == null) return false;
 
-        // Only allow HTTP and HTTPS pages, as that is these are the only scenarios supported by the
-        // background/offline page saving.
-        if (!tab.getUrl().startsWith(UrlConstants.HTTP_SCHEME)
-                && !tab.getUrl().startsWith(UrlConstants.HTTPS_SCHEME)) {
+        // Check if the page url is supported for saving. Only HTTP and HTTPS pages are allowed.
+        if (!OfflinePageBridge.canSavePage(tab.getUrl())) {
             return false;
         }
-        if (tab.isShowingErrorPage()) return false;
+
+        // Download will only be allowed for the error page if download button is shown in the page.
+        if (tab.isShowingErrorPage()) {
+            final OfflinePageBridge bridge = OfflinePageBridge.getForProfile(tab.getProfile());
+            return bridge.isShowingDownloadButtonInErrorPage(tab.getWebContents());

[mmenke, 2017/01/09 20:35:39]

How accurate is this required to be?  It can return true for non-error pages,
and returns the value of the last loaded error from load start through load
commit until load finished.

Tracking page state across processes can get finicky.

[jianli, 2017/01/09 23:35:07]

isShowingDownloadButtonInErrorPage will only be checked after isShowingErrorPage
returns true, which is only true after the error page navigation is committed.
So it means:
* If the page load is not committed, regardless error page or not, we will
continue the flow to do other checks.
* If the error page is committed, isShowingDownloadButtonInErrorPage info should
already been set. We will return true/false accordingly.

I think it is OK not to have the accurate info since the page saving layer
should have its own checking logic.

+        }
+
         if (tab.isShowingInterstitialPage()) return false;
 
         // Don't allow re-downloading the currently displayed offline page.