Only build with _FORTIFY_SOURCE in Release mode.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 3c4547ce0d2b718ed8c7b8c15b6d56a408910391..7363444fd93800d040bf4232abbfbbcac4b03619 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -2266,6 +2266,15 @@
           ['win_use_allocator_shim==0', {
             'defines': ['NO_TCMALLOC'],
           }],
+          ['os_posix==1 and chromium_code==1', {
+            # Non-chromium code is not guaranteed to compile cleanly
+            # with _FORTIFY_SOURCE. Also, fortified build may fail
+            # when optimizations are disabled, so only do that for Release
+            # build.
+            'defines': [
+              '_FORTIFY_SOURCE=2',
+            ],
+          }],
           ['OS=="linux" or OS=="android"', {
             'target_conditions': [
               ['_toolset=="target"', {
@@ -2312,15 +2321,6 @@
           '-Wl,-z,now',
           '-Wl,-z,relro',
         ],
-        'conditions': [
-          ['chromium_code==1', {
-            # Non-chromium code is not guaranteed to compile cleanly
-            # with _FORTIFY_SOURCE.
-            'defines': [
-              '_FORTIFY_SOURCE=2',
-            ],
-          }],
-        ],
       },
     }],
     ['os_posix==1 and OS!="mac" and OS!="ios"', {