Pull GN @ 252040, update calls

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 dce993d5cf42fb1888ddb787f6165a5340c4d990..e6c3e126485c989fcd930896eb2760df0f59d71d 100644
--- a/build/config/ios/ios_sdk.gni
+++ b/build/config/ios/ios_sdk.gni
@@ -8,25 +8,20 @@ declare_args() {
   ios_sdk_path = ""
 
   # Set to true when targeting a simulator build on iOS. False means that the
-  # target is for running on the device. The default value (the empty string)
-  # means to pick the default based on the generator.
-  use_ios_simulator = ""
+  # target is for running on the device. The default value is to use the
+  # Simulator except when targeting GYP's Xcode builds (for compat with the
+  # existing GYP build).
+  use_ios_simulator = !is_gyp_xcode_generator
 
   # Version of iOS that we're targeting.
   ios_deployment_target = "6.0"
 }
 
-if (use_ios_simulator == "") {
-  # Pick the default based on the generator. Currently, the Ninja build only
-  # supports the simulator, while we default to device builds on Xcode.
-  use_ios_simulator = !is_gyp_xcode_generator
-} else {
-  # Simulator flag explicitly passed in.
-  if (!is_gyp_xcode_generator) {
-    # The Ninja build currently only targets the simulator.
-    assert(use_ios_simulator,
-           "You can't do an iOS device build using Ninja yet.")
-  }
+# Simulator flag explicitly passed in.
+if (!is_gyp_xcode_generator) {
+  # The Ninja build currently only targets the simulator.
+  assert(use_ios_simulator,
+         "You can't do an iOS device build using Ninja yet.")
 }
 
 if (ios_sdk_path == "") {