Re-implement UserAgent in browser

- Remove calls to SWE's WebSetting API and use the newer implementation of
  the engine. The newer implementation tracks UserAgent per navigation
  entry.
- Allow to override the UserAgent using command line switches.
- Remove debug option to change UserAgent string.
- BrowserConfig class cleanup.

Change-Id: Ib1cc4763e0cbf0207793d1f4e6b1644a9dbb5c08
diff --git a/src/com/android/browser/EngineInitializer.java b/src/com/android/browser/EngineInitializer.java
index 10cbc0d..7fa7b2a 100644
--- a/src/com/android/browser/EngineInitializer.java
+++ b/src/com/android/browser/EngineInitializer.java
@@ -202,6 +202,8 @@
         if (!mInitializationCompleted) {
             // TODO: Evaluate the benefit of async Engine.initialize()
             Engine.initialize(ctx);
+            // Add the UA override
+            BrowserConfig.getInstance(ctx).overrideUserAgent();
             //Enable remote debugging by default
             Engine.setWebContentsDebuggingEnabled(true);
             mInitializationCompleted = true;