Introduce shared_memory_support media target for PPAPI

ppapi/native_client/src/shared/ppapi_proxy/plugin_ppb_audio.cc

Index: ppapi/native_client/src/shared/ppapi_proxy/plugin_ppb_audio.cc
diff --git a/ppapi/native_client/src/shared/ppapi_proxy/plugin_ppb_audio.cc b/ppapi/native_client/src/shared/ppapi_proxy/plugin_ppb_audio.cc
index 2a01b97bf2f2c7546d43a6a2419af4d1ba84b884..18558e6370a576a8848024d31cb1264e2047642f 100644
--- a/ppapi/native_client/src/shared/ppapi_proxy/plugin_ppb_audio.cc
+++ b/ppapi/native_client/src/shared/ppapi_proxy/plugin_ppb_audio.cc
@@ -15,6 +15,7 @@
 #include "native_client/src/shared/ppapi_proxy/plugin_resource.h"
 #include "native_client/src/shared/ppapi_proxy/utility.h"
 #include "native_client/src/shared/srpc/nacl_srpc.h"
+#include "media/audio/shared_memory_util.h"
 #include "ppapi/c/ppb_audio.h"
 #include "ppapi/c/ppb_audio_config.h"
 #include "ppapi/cpp/module_impl.h"
@@ -29,19 +30,6 @@ size_t ceil64k(size_t n) {
   return (n + 0xFFFF) & (~0xFFFF);
 }
 
-// The following function SetAudioActualDataSizeInBytes, is copied & similar
-// to the one in audio_util.cc.
-void SetAudioActualDataSizeInBytes(void* audio_buffer,
-                                   uint32_t buffer_size_in_bytes,
-                                   uint32_t actual_size_in_bytes) {
-  char* end = static_cast<char*>(audio_buffer) + buffer_size_in_bytes;
-  DCHECK(0 == (reinterpret_cast<size_t>(end) & 3));
-  volatile uint32_t* end32 = reinterpret_cast<volatile uint32_t*>(end);
-  // Set actual data size at the end of the buffer.
-  __sync_synchronize();
-  *end32 = actual_size_in_bytes;
-}
-
 }  // namespace
 
 PluginAudio::PluginAudio() :
@@ -65,7 +53,8 @@ PluginAudio::~PluginAudio() {
     GetInterface()->StopPlayback(resource_);
   // Unmap the shared memory buffer, if present.
   if (shm_buffer_) {
-    munmap(shm_buffer_, ceil64k(TotalAudioSharedMemorySizeInBytes(shm_size_)));
+    munmap(shm_buffer_,
+           ceil64k(media::TotalSharedMemorySizeInBytes(shm_size_)));
     shm_buffer_ = NULL;
     shm_size_ = 0;
   }
@@ -103,9 +92,9 @@ void PluginAudio::AudioThread(void* self) {
                           audio->user_data_);
     // Signal audio backend by writing buffer length at end of buffer.
     // (Note: NaCl applications will always write the entire buffer.)
-    SetAudioActualDataSizeInBytes(audio->shm_buffer_,
-                                  audio->shm_size_,
-                                  audio->shm_size_);
+    media::SetActualDataSizeInBytes(audio->shm_buffer_,
+                                    audio->shm_size_,
+                                    audio->shm_size_);
   }
 }
 
@@ -117,7 +106,7 @@ void PluginAudio::StreamCreated(NaClSrpcImcDescType socket,
   shm_ = shm;
   shm_size_ = shm_size;
   shm_buffer_ = mmap(NULL,
-                     ceil64k(TotalAudioSharedMemorySizeInBytes(shm_size)),
+                     ceil64k(media::TotalSharedMemorySizeInBytes(shm_size)),
                      PROT_READ | PROT_WRITE,
                      MAP_SHARED,
                      shm,