Add calls to the server to request WebAPK updates.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkInstaller.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkInstaller.java b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkInstaller.java
index fd0629e9ad4b94a5327049be5bd2eb96efba4fad..55a9252e042dc8ab8e1af0541e8e87d9e12287f5 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkInstaller.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/webapps/WebApkInstaller.java
@@ -18,7 +18,7 @@ import java.io.File;
 
 /**
  * Java counterpart to webapk_installer.h
- * Contains functionality to install WebAPKs.
+ * Contains functionality to install / update WebAPKs.
  */
 public class WebApkInstaller {
     private static final String TAG = "WebApkInstaller";
@@ -53,6 +53,18 @@ public class WebApkInstaller {
     }
 
     /**
+     * Updates a WebAPK.
+     * @param filePath File to update.
+     * @param packageName Package name to update WebAPK at.
+     * @return True if the update was started. A "true" return value does not guarantee that the
+     *         update succeeds.
+     */
+    @CalledByNative
+    private static boolean updateAsyncFromNative(String filePath, String packageName) {
+        return false;

[Yaron, 2016/08/12 21:16:16]

i'm confused - why is this disabled? enough moving parts?

[Xi Han, 2016/08/15 21:38:44]

It returns false since I didn't add a logic to update an installed WebAPK. It is
unclear to me whether we installl the downloaded WebAPK. or it is possible to
just "update". Peter has looked into this part.

[Yaron, 2016/08/16 00:32:03]

you have to trigger the install the same way as install does or nothing will
happen. i'm fine doing this as a follow-up though

[Xi Han, 2016/08/16 14:08:14]

Acknowledged. Since this isn't the focus of this CL, will add it in the follow
up one.

+    }
+
+    /**
      * Returns whether the user has enabled installing apps from sources other than the Google Play
      * Store.
      */