Add in macro to abstract the differences in library naming conventions between mac and linux.

media/base/media_posix.cc

Index: media/base/media_posix.cc
diff --git a/media/base/media_posix.cc b/media/base/media_posix.cc
index 51efbca3bc4576a7a37baa479341588e7d38d412..5d529a8e05325592602834b622a384c55306f9f2 100644
--- a/media/base/media_posix.cc
+++ b/media/base/media_posix.cc
@@ -19,18 +19,23 @@ namespace media {
 
 namespace {
 
+#if defined(OS_MACOSX)
+#define DSO_NAME(MODULE, VERSION) ("lib" MODULE "." #VERSION ".dylib")
+#elif defined(OS_LINUX)
+#define DSO_NAME(MODULE, VERSION) ("lib" MODULE ".so." #VERSION)
+#else
+#error Unsupported OS.
+#endif
+
 // Retrieves the DSOName for the given key.
 std::string GetDSOName(tp_ffmpeg::StubModules stub_key) {
-  // TODO(ajwong): Do we want to lock to a specific ffmpeg version?
-  // TODO(port): These library names are incorrect for mac.  We need .dynlib
-  // suffixes.
   switch (stub_key) {
     case tp_ffmpeg::kModuleAvcodec52:
-      return FILE_PATH_LITERAL("libavcodec.so.52");
+      return FILE_PATH_LITERAL(DSO_NAME("avcodec", 52));
     case tp_ffmpeg::kModuleAvformat52:
-      return FILE_PATH_LITERAL("libavformat.so.52");
+      return FILE_PATH_LITERAL(DSO_NAME("avformat", 52));
     case tp_ffmpeg::kModuleAvutil50:
-      return FILE_PATH_LITERAL("libavutil.so.50");
+      return FILE_PATH_LITERAL(DSO_NAME("avutil", 50));
     default:
       LOG(DFATAL) << "Invalid stub module requested: " << stub_key;
       return FILE_PATH_LITERAL("");