Replace base::StaticAtomicSequenceNumber with base::AtomicSequenceNumber in //media

after a refactoring at http://crrev.com/ad6d8a9bbf9bd5e2.
As a follow-up of the refactoring, this CL inlines the alias to its users
in //media

base: :StaticAtomicSequenceNumber is an alias of base::AtomicSequenceNumber
Change-Id: Ifed4e77d7b0af0ee1ed084b9aed72be4503694c3
Reviewed-on: https://chromium-review.googlesource.com/568198
Commit-Queue: Taiju Tsuiki <tzik@chromium.org>
Reviewed-by: Xiaohan Wang <xhwang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486285}

media/base/media_log.cc

@@ -15,7 +15,7 @@ namespace media {
 
 // A count of all MediaLogs created in the current process. Used to generate
 // unique IDs.
-static base::StaticAtomicSequenceNumber g_media_log_count;
+static base::AtomicSequenceNumber g_media_log_count;
 
 std::string MediaLog::MediaLogLevelToString(MediaLogLevel level) {
   switch (level) {

media/base/video_frame.cc

@@ -33,8 +33,8 @@ gfx::Rect Intersection(gfx::Rect a, const gfx::Rect& b) {
 
 }  // namespace
 
-// Static POD class for generating unique identifiers for each VideoFrame.
-static base::StaticAtomicSequenceNumber g_unique_id_generator;
+// Static constexpr class for generating unique identifiers for each VideoFrame.
+static base::AtomicSequenceNumber g_unique_id_generator;
 
 static bool IsPowerOfTwo(size_t x) {
   return x != 0 && (x & (x - 1)) == 0;

media/gpu/vt_video_decode_accelerator_mac.cc

@@ -44,10 +44,10 @@ namespace media {
 namespace {
 
 // A sequence of ids for memory tracing.
-base::StaticAtomicSequenceNumber g_memory_dump_ids;
+base::AtomicSequenceNumber g_memory_dump_ids;
 
 // A sequence of shared memory ids for CVPixelBufferRefs.
-base::StaticAtomicSequenceNumber g_cv_pixel_buffer_ids;
+base::AtomicSequenceNumber g_cv_pixel_buffer_ids;
 
 // Only H.264 with 4:2:0 chroma sampling is supported.
 const VideoCodecProfile kSupportedProfiles[] = {