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..1f02e8aa01cd9a6aceedf7515cc97283f0bac24b 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
@@ -146,15 +146,13 @@ public class WebApkActivity extends WebappActivity {
     }
 
     @Override
-    public void finishNativeInitialization() {
-        super.finishNativeInitialization();
-
-        // TODO(hanxi): Ask WebApk's update manager whether to check resource updates.
+    public void onDeferredStartup() {
+        super.onDeferredStartup();
         if (mManifestUpgradeDetector == null) {

[Yaron, 2016/08/10 02:26:28]

It's a little strange the the activity news up a ManifestUpgradeDetector but
then never does anything with it - it just hands it off to WebApkUpdateManager.
And then ManifestUpgradeDetector internally knows which exact function to call
on WebApkUpdateManager. It seems like all three classes are tightly coupled.

Perhaps another way to approach this to instead have a lazily constructed (not
just static) WebApkUpdateManager (WAUM). It could be owned by ChromeApplication.
 When a WebApkActivity is resumed, it registers with the WAUM which then
indicates to the WAUM to kick off a check. If the activity is stopped, it tells
the WAUM to stop for that.

Then WAUM, could own the WAUM and pass a callback to it when it's completed some
work on its behalf. This would mean:
- WebApkActivity depends on WAUM and not ManifestUpgradeDetector (which was an
implementation detail)
- WAUM knows how to check storage and use MUD to monitor for updates
- MUD doesn't depend on WAUM

One aspect I don't like is it's adding more stuff to ChromeApplication. :/

At a minimum, it's not a "..UpdateManager" as-is and is just "...UpdateUtils"
(it doesn't keep any state) so should be renamed if we don't change this

What do you both think of this?

[Xi Han, 2016/08/11 19:01:13]

As discussed offline, adopted the above solution.

             mManifestUpgradeDetector =
                     new ManifestUpgradeDetector(getActivityTab(), mWebappInfo);
         }
-        mManifestUpgradeDetector.start();
+        WebApkUpdateManager.checkUpdate(mWebappInfo.id(), mManifestUpgradeDetector);
     }
 
     @Override