Fix compilation of rtc_base_objc on iOS when building as part of Chromium.

webrtc/base/base.gyp

Index: webrtc/base/base.gyp
diff --git a/webrtc/base/base.gyp b/webrtc/base/base.gyp
index 3e89991fb8d78ebdb59412e30a9c182187590b2f..a4e6bdc9d1af85670d0ef40424e5c86daa51d905 100644
--- a/webrtc/base/base.gyp
+++ b/webrtc/base/base.gyp
@@ -38,8 +38,6 @@
             'objc/RTCDispatcher.m',
             'objc/RTCFieldTrials.h',
             'objc/RTCFieldTrials.mm',
-            'objc/RTCFileLogger.h',
-            'objc/RTCFileLogger.mm',
             'objc/RTCLogging.h',
             'objc/RTCLogging.mm',
             'objc/RTCMacros.h',
@@ -64,6 +62,12 @@
                 },
               },
             }],
+            ['build_with_chromium==0', {
+              'sources': [
+                'objc/RTCFileLogger.h',
+                'objc/RTCFileLogger.mm',
+              ],
+            }],
           ],
         }
       ],