Fix ARM and add -fvisibility=hidden back to libvpx since its linked statically.

libvpx.gyp

Index: libvpx.gyp
===================================================================
--- libvpx.gyp	(revision 97071)
+++ libvpx.gyp	(working copy)
@@ -148,19 +148,6 @@
               'source/libvpx',
             ],
           },
-          'cflags!': [
-            # Ensure the symbols are exported since this library gets wrapped by
-            # ffmpeg's shared lib.  When we stop doing that (crbug.com/70687)
-            # this can go away.
-            '-fvisibility=hidden',
-          ],
-          'conditions': [
-            [ 'OS=="mac"', {
-              'xcode_settings': {
-                'GCC_SYMBOLS_PRIVATE_EXTERN': 'NO',  # No -fvisibility=hidden
-              },
-            }],
-          ],
           'rules': [
             {
               'rule_name': 'assemble',
@@ -392,16 +379,15 @@
             # generated to.
             '-Wa,-I,third_party/libvpx/source/config/<(OS)/<(target_arch_full)',
           ],
-          'cflags!': [
-            # Ensure the symbols are exported since this library gets wrapped by
-            # ffmpeg's shared lib.  When we stop doing that (crbug.com/70687)
-            # this can go away.
-            '-fvisibility=hidden',
-          ],
           'include_dirs': [
             'source/config/<(OS)/<(target_arch_full)',
             'source/libvpx',
           ],
+          'direct_dependent_settings': {
+            'include_dirs': [
+              'source/libvpx',
+            ],
+          },
           'sources': [
             '<@(libvpx_generic_sources)',
             # Generated by ./source/configure and checked in.