Remove som GYP annotations, remove unused manifest.

chromecast/browser/android/BUILD.gn

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import("//build/config/android/rules.gni")
 
 assert(is_android)
 
-# GYP target: chromecast.gyp:cast_shell_manifest
 jinja_template("cast_shell_manifest") {
   input = "apk/AndroidManifest.xml.jinja2"
   output = "$root_gen_dir/cast_shell_manifest/AndroidManifest.xml"
 }
 
-# GYP target: n/a
 android_resources("cast_shell_android_resources") {
   android_manifest = "$root_gen_dir/cast_shell_manifest/AndroidManifest.xml"
   android_manifest_dep = ":cast_shell_manifest"
   resource_dirs = [ "//chromecast/browser/android/apk/res" ]
 }
 
-# GYP target: chromecast.gyp:cast_shell_java
 android_library("cast_shell_java") {
   java_src_dir = "//chromecast/browser/android/apk/src"
   java_files = [
     "$java_src_dir/org/chromium/chromecast/shell/CastApplication.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastAudioManager.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastBrowserHelper.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastCrashHandler.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastCrashUploader.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastMetricsHelper.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastShellActivity.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastSysInfoAndroid.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastWindowAndroid.java",
     "$java_src_dir/org/chromium/chromecast/shell/CastWindowManager.java",
   ]
 
   deps = [
     ":cast_shell_android_resources",
     "//base:base_java",
     "//chromecast/base:base_java",
     "//content/public/android:content_java",
     "//media/base/android:media_java",
     "//net/android:net_java",
 
     # TODO(slan): We may need to pass this in as a parameter.
     "//third_party/android_tools:android_support_v4_java",
     "//ui/android:ui_java",
   ]
 }