Add calls to the server to request WebAPK updates.

chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkActivity.java

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkActivity.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkActivity.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkActivity.java
index 7c4a070defd51917c2f13376bbf5e96ed1f2895e..4432c5c06b31c975cef71877bbb4c6992530d913 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkActivity.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkActivity.java
@@ -5,6 +5,7 @@
 package org.chromium.chrome.browser.webapps;
 
 import android.content.Intent;
+import android.os.AsyncTask;
 
 import org.chromium.base.ContextUtils;
 import org.chromium.base.library_loader.LibraryProcessType;
@@ -149,12 +150,17 @@ public class WebApkActivity extends WebappActivity {
     public void finishNativeInitialization() {
         super.finishNativeInitialization();
 
-        // TODO(hanxi): Ask WebApk's update manager whether to check resource updates.
-        if (mManifestUpgradeDetector == null) {
-            mManifestUpgradeDetector =
-                    new ManifestUpgradeDetector(getActivityTab(), mWebappInfo);
-        }
-        mManifestUpgradeDetector.start();
+        new AsyncTask<Void, Void, Void>() {
+            @Override
+            protected Void doInBackground(Void... nothing) {
+                if (mManifestUpgradeDetector == null) {
+                    mManifestUpgradeDetector =
+                            new ManifestUpgradeDetector(getActivityTab(), mWebappInfo);
+                }
+                WebApkUpdateManager.checkUpdate(mWebappInfo.id(), mManifestUpgradeDetector);

[pkotwicz, 2016/08/08 18:59:15]

I just talked to Yaron. He said that it is OK for us to call
WebApkUpdateManager.checkUpdate() on the UI thread. If I understand correctly,
AsyncTasks are for expensive things such as encoding a Bitmap. I don't think
that WebApkUpdateManager does anything expensive.
WebappRegistry#getWebappDataStorage() already kicks off an Async task.

ShortcutHelper::AddToLauncherInBackgroundWithSkBitmap() does a bunch of
non-expensive things on the IO thread. I am going to change this so that only
the expensive things are done on a background thread.

[Xi Han, 2016/08/08 21:25:05]

As a second thought, move the call of |callUpdate| to onDeferredStartup() and
call it on UI thread. It won't delay the launching of WebAPK any longer.

+                return null;
+            }
+        }.execute();
     }
 
     @Override