GN iOS build fixes.

build/gyp_chromium

Index: build/gyp_chromium
diff --git a/build/gyp_chromium b/build/gyp_chromium
index 9353752f6514d055058fd09507b688e067a0979f..6ab07d6db498ad0b7a4058546d7dce165891b1fc 100755
--- a/build/gyp_chromium
+++ b/build/gyp_chromium
@@ -233,14 +233,14 @@ def GetArgsStringForGN(supplemental_files):
   if 'gomadir' in vars_dict:
     gn_args += ' goma_dir=%s' % EscapeStringForGN(vars_dict['gomadir'])
 
-  # Clear the "use_ios_simulator" flag if the ios_sdk_path is set and is
-  # not a simulator SDK. This duplicates code done in GYP's xcode emulation.
+  # Set the "use_ios_simulator" flag if the ios_sdk_path is set.
   if 'ios_sdk_path' in vars_dict:
-    if not os.path.basename(vars_dict['ios_sdk_path']).lower().startswith(
+    if os.path.basename(vars_dict['ios_sdk_path']).lower().startswith(
         'iphonesimulator'):
+      gn_args += ' use_ios_simulator=true'
+    else:
       gn_args += ' use_ios_simulator=false'
 
-
   # These arguments get passed directly as integers (avoiding the quoting and
   # escaping of the string ones above).
   for v in ['arm_version']: