Browser: add to support search engine preset

1. Set Baidu search engine as the default search engine.
2. Add 139 search engine for carrier.

CRs-fixed: 507955

Change-Id: Idccc86f2d9ac439dcfff5f65e853bb4618fed361
diff --git a/src/com/android/browser/BrowserSettings.java b/src/com/android/browser/BrowserSettings.java
index 17e2001..0b415be 100644
--- a/src/com/android/browser/BrowserSettings.java
+++ b/src/com/android/browser/BrowserSettings.java
@@ -757,7 +757,11 @@
     // -----------------------------
 
     public String getSearchEngineName() {
-        return mPrefs.getString(PREF_SEARCH_ENGINE, SearchEngine.GOOGLE);
+        String defaultSearchEngineValue = mContext.getString(R.string.default_search_engine_value);
+        if (defaultSearchEngineValue == null) {
+            defaultSearchEngineValue = SearchEngine.GOOGLE;
+        }
+        return mPrefs.getString(PREF_SEARCH_ENGINE, defaultSearchEngineValue);
     }
 
     public boolean allowAppTabs() {