Add variables to simplify code signing on iOS.

build/config/ios/ios_sdk.gni

Index: build/config/ios/ios_sdk.gni
diff --git a/build/config/ios/ios_sdk.gni b/build/config/ios/ios_sdk.gni
index 0a3cded59cf1661546695f3a589ae8ad7057f0e4..687652d5f645cf454959f10ad8f1a0f8ce0a5397 100644
--- a/build/config/ios/ios_sdk.gni
+++ b/build/config/ios/ios_sdk.gni
@@ -25,6 +25,17 @@ declare_args() {
   ios_enable_code_signing = true
   ios_code_signing_identity = ""
 
+  # Prefix for CFBundleIdentifier property in iOS application bundles. You
+  # need to have code signing identity and mobile provisioning profiles that
+  # can sign $ios_app_bundle_id_prefix.* to build and run the app on devices.
+  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 free certificates.

[justincohen, 2016/10/19 17:28:10]

We aren't requiring developers to use a free account, they can still use dev or
enterprise paid accounts.  Instead can we say something to the effect:

 ... same bundle id to avoid running out of certificates if using a free
account.

The title should change as well, something like '... configure app bundle id
prefix and to enable automatically managed certs.'

Apologies if I created this confusion when I put text in the bug!

+  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.