Disable FullStackTest.LargeRoomVP8_*thumb on iOS

It fails for the same reason as on Android

BUG=webrtc:7301

Review-Url: https://codereview.webrtc.org/3017473002
Cr-Commit-Position: refs/heads/master@{#19857}
diff --git a/video/full_stack_tests.cc b/video/full_stack_tests.cc
index ddbed59..ea1e37f 100644
--- a/video/full_stack_tests.cc
+++ b/video/full_stack_tests.cc
@@ -779,8 +779,8 @@
   RunTest(large_room);
 }
 
-#if defined(WEBRTC_ANDROID)
-// Fails on Android:
+#if defined(WEBRTC_ANDROID) || defined(WEBRTC_IOS)
+// Fails on mobile devices:
 // https://bugs.chromium.org/p/webrtc/issues/detail?id=7301
 #define MAYBE_LargeRoomVP8_50thumb DISABLED_LargeRoomVP8_50thumb
 #define MAYBE_LargeRoomVP8_15thumb DISABLED_LargeRoomVP8_15thumb