Fix running gn gen for //ui/* targets on iOS.

ui/gfx/BUILD.gn

Index: ui/gfx/BUILD.gn
diff --git a/ui/gfx/BUILD.gn b/ui/gfx/BUILD.gn
index a5f095e469f0eb2952eb1bc1d69211278b90fb04..94e93c7248b985286fc0b326e4eaadf14e89a1dd 100644
--- a/ui/gfx/BUILD.gn
+++ b/ui/gfx/BUILD.gn
@@ -506,7 +506,6 @@ test("gfx_unittests") {
       "range/range_mac_unittest.mm",
       "range/range_unittest.cc",
       "range/range_win_unittest.cc",
-      "render_text_unittest.cc",
       "sequential_id_generator_unittest.cc",
       "shadow_value_unittest.cc",
       "skbitmap_operations_unittest.cc",
@@ -516,6 +515,10 @@ test("gfx_unittests") {
     ]
   }
 
+  if (!is_android && !is_ios) {

[danakj, 2015/07/22 18:26:23]

This looks the same as before? Why are you changing it?

[Dirk Pranke, 2015/07/22 18:49:36]

I think you're right that this is the same as before, logically. 

In GN code we've moved more to an additive style where 
we try to only list sources in += blocks, especially when we
can't count on sources_assignment_filter to strip them out.

However, such a change isn't required and we're not going
back through all of the code necessarily to rewrite things.

So I think this change is a win but only a minor one.

[sdefresne, 2015/07/23 07:38:03]

It is not identical, the previous code was (summarized):

if (!is_ios) {
  sources + = [ "render_text_unittest.cc" ]
}

if (is_android || is_ios) {
  sources -= [ "render_text_unittest.cc" ]
}

The second conditional was causing failures on iOS since it tried to remove a
file that was not in the sources list. My change uses the additive style.

+    sources += [ "render_text_unittest.cc" ]
+  }
+
   # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
   configs += [ "//build/config/compiler:no_size_t_to_int_warning" ]
 
@@ -549,13 +552,9 @@ test("gfx_unittests") {
     ]
   }
 
-  if (is_android || is_ios) {
-    sources -= [ "render_text_unittest.cc" ]
-  }
-
   if (use_aura) {
     sources -= [ "screen_unittest.cc" ]
-  } else {
+  } else if (!is_ios) {
     sources -= [ "nine_image_painter_unittest.cc" ]
   }