Fix enable_cardboard/enable_cast for GN build of remoting/android.

This makes the settings into proper GN args that can be overridden.
Also added "remoting" to their names since they are remoting-specific.
Also fixed the Cardboard-enabled build (code was expecting '1'/'0' but
GN was supplying 'true'/'false').

Review URL: https://codereview.chromium.org/1637093002

Cr-Commit-Position: refs/heads/master@{#371602}

remoting/android/BUILD.gn

@@ -70,7 +70,11 @@ remoting_localize("remoting_apk_manifest") {
     "java/AndroidManifest.xml.jinja2",
   ]
   locales = [ "en" ]
-  defines = [ "ENABLE_CARDBOARD=$enable_cardboard" ]
+  if (remoting_enable_cardboard) {
+    defines = [ "ENABLE_CARDBOARD=1" ]
+  } else {
+    defines = [ "ENABLE_CARDBOARD=0" ]
+  }
   variables = [ branding_path ]
   output = "$root_gen_dir/remoting/android/{{source_name_part}}"
 }

remoting/android/client_java_tmpl.gni

@@ -10,7 +10,7 @@ template("remoting_android_client_java_tmpl") {
     DEPRECATED_java_in_dir = "//remoting/android/java/src"
     java_files = []
 
-    if (enable_cast) {
+    if (remoting_enable_cast) {
       java_files += [ "//remoting/android/cast/src/org/chromium/chromoting/CastExtensionHandler.java" ]
     }
 

remoting/remoting_options.gni

@@ -11,17 +11,17 @@ declare_args() {
 
   # Set this to enable building internal AppRemoting apps.
   enable_internal_app_remoting_targets = false
-}
 
-# Set this to enable cast mode on the android client.
-enable_cast = false
+  # Set this to enable cast mode on the android client.
+  remoting_enable_cast = false
+
+  # Set this to enable Android Chromoting Cardboard Activity.
+  remoting_enable_cardboard = false
+}
 
 # Set this to use GCD instead of the remoting directory service.
 remoting_use_gcd = 0
 
-# Set this to enable Android Chromoting Cardboard Activity.
-enable_cardboard = false
-
 # Enable the multi-process host on Windows by default.
 if (is_win) {
   remoting_multi_process = 1