Change defaults for build args to accommodate Flutter and Fuchsia.

sdk/BUILD.gn

 # Copyright (c) 2017, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 # This GN file contains build rules for assembling the Dart SDK. There are
 # two possible variants: the "Full" SDK, and the "Platform" SDK. If you want
 # to make a new subset of the Full SDK, make it the same way we make
 # the Platform SDK.
 #
 # Warning:
 # If you need to copy something into dart-sdk/lib/foo in addition to the stuff
 # copied there by :copy_libraries, then you must depend on ":copy_libraries",
 # or ":copy_libraries" may delete/overwrite your addition, and the build will
 # fail.
 
 import("../build/copy_tree.gni")
+import("../build/flutter_args.gni")
 
 declare_args() {
   # Build a SDK with less stuff. It excludes dart2js, ddc, and web libraries.
   dart_platform_sdk = false

[zra, 2017/08/07 22:11:14]

Sorry for not noticing this sooner: Since both Flutter and Fuchsia want the
platform SDK, and only the standalone Dart SDK build wants the full SDK, I think
it makes sense to switch the default sense of this flag to true. Then we can
pass 'false' by default from our //tools/gn.py (except for the architectures
listed below). This way, we can avoid the need to add an is_flutter GN argument.

[aam, 2017/08/07 23:19:07]

tools/gn.py pulls the value for this flag from environment variable
DART_MAKE_PLATFORM_SDK, which is then being overriden with command line argument
--platform-sdk. Changing the default will require renaming those to
DART_MAKE_FULL_SDK and --full-sdk respectively and updating the places where
they are (do we know where are they used? I was not able to find ) Is it worth
it? 

 }
 
 if (is_fuchsia ||
     is_fuchsia_host ||
+    is_flutter ||
     current_cpu == "arm64" ||
     current_cpu == "arm") {
   dart_platform_sdk = true
 }
 
 # The directory layout of the SDK is as follows:
 #
 # ..dart-sdk/
 # ....bin/
 # ......dart or dart.exe (executable)
@@ skipping 184 matching lines @@
 copy("copy_dart") {
   visibility = [ ":create_common_sdk" ]
   deps = [
     "../runtime/bin:dart",
   ]
   dart_out = get_label_info("../runtime/bin:dart", "root_out_dir")
   if (is_win) {
     sources = [
       "$dart_out/dart.exe",
     ]
-  } else if (is_fuchsia || is_fuchsia_host) {
+  } else if (is_fuchsia || is_fuchsia_host || is_flutter) {

[zra, 2017/08/07 22:11:13]

As with the platform_sdk flag, we should change this case to be the default with
a GN flag, like dart_stripped_binary_path = "". Then //tools/gn.py can override
it to "exe.stripped/".

     sources = [
       "$dart_out/dart",
     ]
   } else {
     sources = [
       "$dart_out/exe.stripped/dart",
     ]
   }
   if (is_win) {
     sources += [ "$dart_out/dart.lib" ]
@@ skipping 543 matching lines @@
 group("create_sdk") {
   deps = [
     ":create_common_sdk",
   ]
   if (dart_platform_sdk) {
     deps += [ ":create_platform_sdk" ]
   } else {
     deps += [ ":create_full_sdk" ]
   }
 }