recipes: Add a GN flavor.

infra/bots/recipe_modules/skia/gn_flavor.py

+# 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 default_flavor
+
+"""GN flavor utils, used for building Skia with GN."""
+class GNFlavorUtils(default_flavor.DefaultFlavorUtils):
+  def compile(self, target):
+    """Build Skia with GN."""
+    # Get the gn executable.
+    fetch_gn = self._skia_api.skia_dir.join('bin', 'fetch_gn')
+    self._skia_api.run(self._skia_api.m.step, 'fetch-gn', cmd=[fetch_gn],
+                       cwd=self._skia_api.skia_dir)
+
+    out_dir = 'out/%s' % self._skia_api.configuration

[borenet, 2016/07/28 14:23:27]

use self.out_dir instead

[jcgregorio, 2016/07/28 15:26:25]

Done.

+
+    is_debug = 'is_debug=true'
+    if self._skia_api.configuration != 'Debug':
+        is_debug = 'is_debug=false'
+    gn_args = [is_debug]
+
+    # Run gn gen.
+    gn_exe = 'gn'
+    if self._skia_api.m.platform.is_win:
+        gn_exe = 'gn.exe'
+    gn_gen = [gn_exe, 'gen', out_dir, '--args=%s' % ' '.join(gn_args)]

[mtklein, 2016/07/28 14:25:10]

I suspect when we have more than one, we'll want

 --args="%s"

but we'll find out for sure next time we try to set an arg.

[jcgregorio, 2016/07/28 15:26:25]

I was thinking args would just get added to gn_args, but we'll see how that
works as we add more args.

[mtklein, 2016/07/28 15:30:11]

Yeah, I'm on board there.  I was worried about the ' '.join() part.

If we had gn_args = [ 'is_debug=true', 'cc=clang', 'cxx=clang++' ], we'd get 
'--args=is_debug=true cc=clang cxx=clang++'.  Is GN cool with that?

[jcgregorio, 2016/07/28 15:33:16]

Yeah, it is, I copied this from the pdfium flavor which does the same thing,
which I also initially found surprising.

+    self._skia_api.run(self._skia_api.m.step, 'gn_gen', cmd=gn_gen,
+                       cwd=self._skia_api.skia_dir)
+
+    # Run ninja.
+    ninja_cmd = ['ninja', '-C', out_dir]

[borenet, 2016/07/28 14:23:27]

'ninja' probably needs to be 'ninja.exe' on Windows, but maybe that can wait.

[jcgregorio, 2016/07/28 15:26:25]

Windows can wait.

+    self._skia_api.run(self._skia_api.m.step, 'compile %s' % target,
+            cmd=ninja_cmd,
+            cwd=self._skia_api.skia_dir)