Add yasm and ffmpeg into the build tree for linux.

DEPS

 vars = {
   "webkit_trunk":
     "http://svn.webkit.org/repository/webkit/trunk",
   "webkit_revision": "50258",
   "ffmpeg_revision": "30374",
 }
 
 deps = {
   "src/breakpad/src":
     "http://google-breakpad.googlecode.com/svn/trunk/src@417",
@@ skipping 123 matching lines @@
       "/trunk/deps/third_party/ffmpeg/binaries/mac@" + Var("ffmpeg_revision"),
     "src/third_party/ffmpeg/binaries/chromium/mac/ia32_dbg":
       "/trunk/deps/third_party/ffmpeg/binaries/mac_dbg@" +
       Var("ffmpeg_revision"),
   },
   "unix": {
     # Linux, really.
     "src/third_party/xdg-utils":
       "/trunk/deps/third_party/xdg-utils@29103",
 
+    "src/third_party/yasm/source/patched-yasm":
+      "/trunk/deps/third_party/yasm/patched-yasm@29937",
+
+    "src/third_party/ffmpeg/source/patched-ffmpeg-mt":
+      "/trunk/deps/third_party/ffmpeg/patched-ffmpeg-mt@" +
+      Var("ffmpeg_revision"),
+
     "src/third_party/ffmpeg/binaries/chromium/linux/ia32":
       "/trunk/deps/third_party/ffmpeg/binaries/linux@" +
       Var("ffmpeg_revision"),
     "src/third_party/ffmpeg/binaries/chromium/linux/ia32_dbg":
       "/trunk/deps/third_party/ffmpeg/binaries/linux_dbg@" +
       Var("ffmpeg_revision"),
 
     "src/third_party/ffmpeg/binaries/chromium/linux/x64":
       "/trunk/deps/third_party/ffmpeg/binaries/linux_64@" +
       Var("ffmpeg_revision"),
@@ skipping 50 matching lines @@
                "$matching_files"],
   },
   {
     # Workaround XCode dependecies problem.
     # TODO(bradnelson): remove this when fixed.
     "pattern": ".",
     "action": ["python",
                "src/build/mac/clobber_generated_headers.py"],
   },
 ]