Attempt to head off OmahaClient ANR

* Move code to initialize member variables to when they're actually needed
  by the OmahaClient instead of creating them in onCreate().

* Fully remove the ability to force OmahaClient to send a request to the
  server.  The code that hooked into that was killed ages ago.

BUG=515312

Review URL: https://codereview.chromium.org/1321393002

Cr-Commit-Position: refs/heads/master@{#346770}

chrome/android/java/src/org/chromium/chrome/browser/omaha/VersionNumberGetter.java

@@ -21,10 +21,9 @@ public class VersionNumberGetter {
      * @return The latest version if we retrieved one from the Omaha server, or "" if we haven't.
      */
     public String getLatestKnownVersion(
-            Context applicationContext, String prefPackage, String prefLatestVersion) {
+            Context context, String prefPackage, String prefLatestVersion) {
         assert Looper.myLooper() != Looper.getMainLooper();
-        SharedPreferences prefs = applicationContext.getSharedPreferences(
-                prefPackage, Context.MODE_PRIVATE);
+        SharedPreferences prefs = context.getSharedPreferences(prefPackage, Context.MODE_PRIVATE);
         return prefs.getString(prefLatestVersion, "");
     }
 
@@ -32,7 +31,7 @@ public class VersionNumberGetter {
      * Retrieve the version of Chrome we're using.
      * @return The latest version if we retrieved one from the Omaha server, or "" if we haven't.
      */
-    public String getCurrentlyUsedVersion(Context applicationContext) {
-        return BuildInfo.getPackageVersionName(applicationContext);
+    public String getCurrentlyUsedVersion(Context context) {
+        return BuildInfo.getPackageVersionName(context);
     }
 }