Bring back -fstack-protector-all on iOS.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 0747087c5bc5113e7ffa159121fa453b32b25bc2..9587b665a2423296351da9373254b9df74276a80 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -2821,10 +2821,7 @@
             # TODO(phajdan.jr): Should we enable this for all of POSIX?
             'defines': ['_GLIBCXX_DEBUG=1',],
           }],
-          # Disabled on iOS because it was causing a crash on startup.
-          # TODO(michelea): investigate, create a reduced test and possibly
-          # submit a radar.
-          ['release_valgrind_build==0 and OS!="ios"', {
+          ['release_valgrind_build==0', {
             'xcode_settings': {
               'OTHER_CFLAGS': [
                 '-fstack-protector-all',  # Implies -fstack-protector