Move use_webview_internal_framework to android_webview/BUILD.gn

build/config/android/config.gni

 # Copyright 2014 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.
 
 # This file contains common system config stuff for the Android build.
 
 if (is_android) {
   assert(rebase_path("//", root_build_dir) == "../../",
          "Android output directory must be nested 2 levels within src/ (" +
              "e.g.: out-gn/Debug). http://crbug.com/412935")
@@ skipping 90 matching lines @@
 
     # Neither of these should ever be used for release builds since they are
     # somewhat experimental and dx --incremental is known to not produce
     # byte-for-byte identical output.
     assert(!(enable_incremental_dx && !is_debug))
     assert(!(enable_incremental_javac && !is_debug))
 
     # Adds intrumentation to each function. Writes a file with the order that
     # functions are called at startup.
     use_order_profiling = false
-
-    # Use the internal version of the framework to build Android WebView.
-    use_webview_internal_framework = false

[michaelbai, 2016/01/06 03:53:42]

Sorry, I still don't understand what caused the error and why this variable need
to be removed.

From gn help declare_args, 

"Introduces the given arguments into the current scope. If they are
  not specified on the command line or in a toolchain's arguments,
  the default values given in the declare_args block will be used."

IIUC, the default value of use_webview_internal_framework should be defined
here, then, it could be used every where, did I miss something?

[agrieve, 2016/01/06 04:16:04]

Looks like the problem doesn't happen anymore because
8d2e9c0cb301a83e5e700166e3119ca66bb88b75 was reverted ("Port Monochrome to GN").
Maybe this was the reason for the revert?

If you revert the revert, I suspect you'll see the gn gen failure. 

The problem is just that the order is:

1. GN starts parsing //build/android/config.gni
2. GN hits import("//clank/config.gni")
3. //clank/config.gni references use_webview_internal_framework
4. GN hits the declare_args() block which defines  
use_webview_internal_framework

#3 fails because it needs to happen after #4

   }
 
   # Host stuff -----------------------------------------------------------------
 
   # Defines the name the Android build gives to the current host CPU
   # architecture, which is different than the names GN uses.
   if (host_cpu == "x64") {
     android_host_arch = "x86_64"
   } else if (host_cpu == "x86") {
     android_host_arch = "x86"
@@ skipping 122 matching lines @@
   } else if (current_cpu == "x64") {
     android_app_abi = "x86_64"
   } else if (current_cpu == "arm64") {
     android_app_abi = "arm64-v8a"
   } else if (current_cpu == "mips64el") {
     android_app_abi = "mips64"
   } else {
     assert(false, "Unknown Android ABI: " + current_cpu)
   }
 }