Add Fuchsia clang and sdk to DEPS

These use CIPD (from depot_tools) to download packages created by the
Fuchsia team. The .ensure file is passed to `cipd` which currently
include specificiations for the Fuchsia team's build of clang (which,
because it's close to HEAD includes support for targeting Fuchsia), as
well as the Fuchsia SDK.

Both packages are specified as "latest" rather than pinning to a
specific revision. At this early point in the process we don't have any
good reason to pin, but that can be accomplished later by replacing that
with a specific package's SHA1.

Due to the (relatively new) 'condition': 'checkout_fuchsia', this DEPS
step will only be run when .gclient includes 'fuchsia' in the target_os
block at the top_level, e.g.

$ cat .gclient
solutions = [
  { ...  },
]
target_os = ['fuchsia']

Bug: crashpad:196, crashpad:209
Change-Id: Id6d444a1c4450ffde8ee6665ff9720ce454c5cdf
Reviewed-on: https://chromium-review.googlesource.com/786092
Commit-Queue: Scott Graham <scottmg@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>

.gitignore

@@ -10,6 +10,9 @@
 .gdbinit
 /Makefile
 /out
+/third_party/fuchsia/.cipd
+/third_party/fuchsia/clang
+/third_party/fuchsia/sdk
 /third_party/gtest/gtest
 /third_party/gyp/gyp
 /third_party/mini_chromium/mini_chromium

DEPS

@@ -113,6 +113,18 @@ hooks = [
       'buildtools/linux64/gn.sha1',
     ],
   },
+  {
+    'name': 'fuchsia_clang',
+    'pattern': '.',
+    'condition': 'checkout_fuchsia',
+    'action': [
+      'cipd',
+      'ensure',
+      '-ensure-file', 'crashpad/third_party/fuchsia/toolchain.ensure',
+      '-root', 'crashpad/third_party/fuchsia',
+      '-log-level', 'info',
+    ],
+  },
   {
     'name': 'gyp',
     'pattern': '\.gypi?$',

third_party/fuchsia/README.crashpad

@@ -0,0 +1,4 @@
+This directory is a placeholder for Fuchsia tools that will be downloaded by
+CIPD (https://github.com/luci/luci-go/tree/master/cipd). The toolchain.ensure
+files specifies which CIPD packages to retrieve, at which versions, and where
+they're stored locally. The CIPD update happens as part of gclient runhooks.

third_party/fuchsia/toolchain.ensure

@@ -0,0 +1,19 @@
+# Copyright 2017 The Crashpad Authors. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+@Subdir clang
+fuchsia/clang/${os}-${arch} latest
+
+@Subdir sdk
+fuchsia/sdk/${os=linux}-${arch} latest