Make sure all .a files get loaded by the linker

This ensures their symbols get exported.

chromium_content.gyp

@@ -6,6 +6,11 @@
       'dependencies': [
         'vendor/chromium/src/content/content.gyp:content',
       ], 
+      'xcode_settings': {
+        'OTHER_LDFLAGS': [
+          '-all_load',
+        ],
+      },
     },
   ],
 }