Add variable to conditionally fetch ios_internal.

Add variable checkout_ios_internal to conditionally fetch ios_internal.
Use pinned revision to ensure build stays hermetic and reproducible.

Bug: 803846
Change-Id: Id8ba650400b283645f8c00629dd269739d813195
Reviewed-on: https://chromium-review.googlesource.com/880903
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: Michael Moss <mmoss@chromium.org>
Reviewed-by: John Budorick <jbudorick@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#532437}

DEPS

@@ -49,6 +49,10 @@ vars = {
   # custom_vars.
   'checkout_src_internal': False,
 
+  # By default, do not check out Google's internal dependencies. This can be
+  # overridden e.g. with custom_vars.
+  'checkout_google_internal': False,
+
   # Fetch the additional packages and files needed to run all of the
   # telemetry tests. This is false by default as some stuff is only
   # privately accessible.
@@ -247,6 +251,11 @@ deps = {
       'condition': 'checkout_ios',
   },
 
+  'src/ios_internal': {
+      'url': 'https://chrome-internal.googlesource.com/chrome/ios_internal.git' + '@' + '3fd2cebe6fc1ccd43675a23d492c323aa42e3b81',
+      'condition': 'checkout_ios and checkout_google_internal',
+  },
+
   'src/media/cdm/api':
     Var('chromium_git') + '/chromium/cdm.git' + '@' + 'ca7130aa8fe6dd6c0664b52768d1957af31ae91b',
 
@@ -1369,4 +1378,8 @@ recursedeps = [
   ("src/third_party/angle", "DEPS.chromium"),
   # src-internal has its own DEPS file to pull additional internal repos
   'src-internal',
+  # src/ios_internal has its own DEPS file (named DEPS.chromium until the
+  # transition to gclient conditions is complete, see http://crbug.com/803846
+  # for progress).
+  ('src/ios_internal', 'DEPS.chromium'),
 ]