Remove override of C standard on iOS/macOS.

The CL https://chromium-review.googlesource.com/578630 configured
all platform to use C11 but did not remove the code enabling C99
on iOS/macOS. This caused iOS/macOS to use an older standard.

Bug: 766484
Change-Id: I31090257abe4feb770a0b088cfa657e2b42ca624
Reviewed-on: https://chromium-review.googlesource.com/671349
Reviewed-by: Robert Sesek <rsesek@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#502832}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 7b0bfa078e3aff89974e6772cf2fa4e670e4f136

config/ios/BUILD.gn

@@ -64,9 +64,6 @@ config("compiler") {
   # an Objective C struct won't be called, which is very bad.
   cflags_objcc = [ "-fobjc-call-cxx-cdtors" ]
 
-  cflags_c = [ "-std=c99" ]
-  cflags_objc = cflags_c
-
   ldflags = common_ios_flags
 }
 

config/mac/BUILD.gn

@@ -37,9 +37,6 @@ config("compiler") {
   # an Objective C struct won't be called, which is very bad.
   cflags_objcc = [ "-fobjc-call-cxx-cdtors" ]
 
-  cflags_c = [ "-std=c99" ]
-  cflags_objc = cflags_c
-
   ldflags = common_mac_flags
 
   if (save_unstripped_output) {