Add variables to simplify code signing on iOS.

Add variables to configure the generated bundle identifier prefix (known
as "Organization Identifier" in Xcode) and to enable automatically managed
certs.

Those variables are currently unused in order to avoid breaking the iOS
downstream tree when they land. Once the Chrome on iOS private code has
been updated to override them, they will be connected to the build.

BUG=613543

Review-Url: https://chromiumcodereview.appspot.com/2431423002
Cr-Original-Commit-Position: refs/heads/master@{#426293}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: ff5bbc987d0d57f509a6d191285c9c4c8729ff58

config/ios/ios_sdk.gni

@@ -23,6 +23,17 @@ declare_args() {
   ios_enable_code_signing = true
   ios_code_signing_identity = ""
 
+  # Prefix for CFBundleIdentifier property of iOS bundles (correspond to the
+  # "Organization Identifier" in Xcode). Code signing will fail if no mobile
+  # provisioning for the selected code signing identify support that prefix.
+  ios_app_bundle_id_prefix = "org.chromium"
+
+  # If true, then allow using Xcode to automatically manage certificates. This
+  # requires loading a separate Xcode project and enable automatically managed
+  # certificates. When true, all test application will use the same bundle id
+  # to avoid running out of certificates if using a free account.
+  ios_automatically_manage_certs = true
+
   # If non-empty, this list must contain valid cpu architecture, and the final
   # build will be a multi-architecture build (aka fat build) supporting the
   # main $target_cpu architecture and all of $additional_target_cpus.