Fix a crash when AsyncTask cannot be scheduled while posting notification updates

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

Index: chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java
index 038878378b11d742ae6a8edbc926da83e9443c7f..f7291c92a0f82af2b64cb2d22ecf89b93d53d40a 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/download/DownloadManagerService.java
@@ -46,8 +46,8 @@ import java.util.HashMap;
 import java.util.HashSet;
 import java.util.Iterator;
 import java.util.List;
-import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.RejectedExecutionException;
 import java.util.concurrent.TimeUnit;
 
 /**
@@ -644,29 +644,26 @@ public class DownloadManagerService extends BroadcastReceiver implements
         if (mIsUIUpdateScheduled) return;
 
         mIsUIUpdateScheduled = true;
-        final List<DownloadProgress> progressToUpdate = new ArrayList<DownloadProgress>();
-        Iterator<Map.Entry<String, DownloadProgress>> iter =
-                mDownloadProgressMap.entrySet().iterator();
+        final List<DownloadProgress> progressPendingUpdate = new ArrayList<DownloadProgress>();
+        Iterator<DownloadProgress> iter = mDownloadProgressMap.values().iterator();
         while (iter.hasNext()) {
-            Map.Entry<String, DownloadProgress> entry = iter.next();
-            DownloadProgress progress = entry.getValue();
+            DownloadProgress progress = iter.next();
             if (progress.mIsUpdated) {
-                progressToUpdate.add(new DownloadProgress(progress));
-                progress.mIsUpdated = false;
-            }
-            // Remove progress entry from  mDownloadProgressMap if they are no longer needed.
-            if ((progress.mDownloadStatus != DOWNLOAD_STATUS_IN_PROGRESS
-                    || progress.mDownloadItem.getDownloadInfo().isPaused())
-                    && (progress.mDownloadStatus != DOWNLOAD_STATUS_INTERRUPTED
-                            || !progress.mIsAutoResumable)) {
-                iter.remove();
+                progressPendingUpdate.add(progress);
             }
         }
-        if (progressToUpdate.isEmpty()) {
+        if (progressPendingUpdate.isEmpty()) {
             mIsUIUpdateScheduled = false;
             return;
         }
-        new AsyncTask<Void, Void, List<DownloadItem>>() {
+        // Make a copy of the |progressUpdated|, so that we can update the notification on another
+        // thread without worrying about concurrent modifications.
+        final List<DownloadProgress> progressToUpdate = new ArrayList<DownloadProgress>();
+        for (int i = 0; i < progressPendingUpdate.size(); ++i) {
+            progressToUpdate.add(new DownloadProgress(progressPendingUpdate.get(i)));
+        }
+        AsyncTask<Void, Void, List<DownloadItem>> task =
+                new AsyncTask<Void, Void, List<DownloadItem>>() {
             @Override
             public List<DownloadItem> doInBackground(Void... params) {
                 return updateAllNotifications(progressToUpdate);
@@ -680,7 +677,25 @@ public class DownloadManagerService extends BroadcastReceiver implements
                             DownloadManager.ERROR_UNKNOWN);
                 }
             }
-        }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+        };
+        try {
+            task.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
+            for (int i = 0; i < progressPendingUpdate.size(); ++i) {
+                DownloadProgress progress = progressPendingUpdate.get(i);
+                progress.mIsUpdated = false;
+                // Remove progress entry from  mDownloadProgressMap if they are no longer needed.
+                if ((progress.mDownloadStatus != DOWNLOAD_STATUS_IN_PROGRESS
+                        || progress.mDownloadItem.getDownloadInfo().isPaused())
+                        && (progress.mDownloadStatus != DOWNLOAD_STATUS_INTERRUPTED
+                                || !progress.mIsAutoResumable)) {
+                    mDownloadProgressMap.remove(progress.mDownloadItem.getId());
+                }
+            }
+        } catch (RejectedExecutionException e) {
+            // Reaching thread limit, update will be reschduled for the next run.
+            Log.e(TAG, "reaching thread limit, reschedule notification update later.");
+        }
+
         Runnable scheduleNextUpdateTask = new Runnable(){
             @Override
             public void run() {