Suppress deprecation warnings in video_capture for iOS

The chromium_revision roll in r6913 broke the iOS build since the
videoMinFrameDuration and videoMaxFrameDuration properties
have been deprecated in iOS 7.0, which is now the default target
platform for iOS.

BUG=3705
TEST=Passing ios and ios_rel trybots.
TBR=tkchin@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/22389004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@6914 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/modules/video_capture/video_capture.gypi b/webrtc/modules/video_capture/video_capture.gypi
index dced22c..7382a1c 100644
--- a/webrtc/modules/video_capture/video_capture.gypi
+++ b/webrtc/modules/video_capture/video_capture.gypi
@@ -116,6 +116,12 @@
               ],
               'xcode_settings': {
                 'CLANG_ENABLE_OBJC_ARC': 'YES',
+                'WARNING_CFLAGS':  [
+                  # To avoid warnings for deprecated videoMinFrameDuration and
+                  # videoMaxFrameDuration properties in iOS 7.0.
+                  # See webrtc:3705 for more details.
+                  '-Wno-deprecated-declarations',
+                ],
               },
               'all_dependent_settings': {
                 'xcode_settings': {