[Android] Add the Contextual Search enable switch.

Adding about:flags toggle to enable Contextual Search in Chrome for Android.

BUG=341337

Review URL: https://codereview.chromium.org/157803002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@249907 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index ebbe6cc..c08171cf 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -727,6 +727,13 @@
     ENABLE_DISABLE_VALUE_TYPE(switches::kEnableNewNTP,
                               switches::kDisableNewNTP)
   },
+  {
+    "contextual-search",
+    IDS_FLAGS_ENABLE_CONTEXTUAL_SEARCH,
+    IDS_FLAGS_ENABLE_CONTEXTUAL_SEARCH_DESCRIPTION,
+    kOsAndroid,
+    SINGLE_VALUE_TYPE(switches::kEnableContextualSearch)
+  },
 #endif
   {
     "show-autofill-type-predictions",