Convert /third_party/ffmpeg to gyp and a python build script.

media/media.gyp

Index: media/media.gyp
diff --git a/media/media.gyp b/media/media.gyp
index 00a46756470ec8d7af81861ccb06127b4128045b..b924a422af2bd51ab4e9bbe124f0372ff5dbafbf 100644
--- a/media/media.gyp
+++ b/media/media.gyp
@@ -22,6 +22,7 @@
       'type': 'static_library',
       'dependencies': [
         '../base/base.gyp:base',
+        '../third_party/ffmpeg/ffmpeg.gyp:ffmpeg',
       ],
       'include_dirs': [
         '..',
@@ -87,13 +88,9 @@
         'filters/video_renderer_base.cc',
         'filters/video_renderer_base.h',
       ],
-      'include_dirs': [
-        '../third_party/ffmpeg/include',
-      ],
       'direct_dependent_settings': {
         'include_dirs': [
           '..',
-          '../third_party/ffmpeg/include',
         ],
       },
       'conditions': [
@@ -117,16 +114,6 @@
             'filters/ffmpeg_video_decoder.cc',
           ],
         }],
-        ['OS =="win"', {
-          'include_dirs': [
-            '../third_party/ffmpeg/include/win',
-          ],
-          'direct_dependent_settings': {
-            'include_dirs': [
-              '../third_party/ffmpeg/include/win',
-            ],
-          },
-        }],
       ],
     },
     {
@@ -184,6 +171,7 @@
           'dependencies': [
             'media',
             '../base/base.gyp:base',
+            '../third_party/ffmpeg/ffmpeg.gyp:ffmpeg',
           ],
           'sources': [
             'player/player.cc',