[PPAPI][MediaStream] Support configure for video input.

ppapi/shared_impl/media_stream_buffer_manager.cc

Index: ppapi/shared_impl/media_stream_buffer_manager.cc
diff --git a/ppapi/shared_impl/media_stream_buffer_manager.cc b/ppapi/shared_impl/media_stream_buffer_manager.cc
index b0588d6df4832540677c8b52fba39ac57610a762..52134678db164ce6e0f518d8423c8e73936a6288 100644
--- a/ppapi/shared_impl/media_stream_buffer_manager.cc
+++ b/ppapi/shared_impl/media_stream_buffer_manager.cc
@@ -31,7 +31,6 @@ bool MediaStreamBufferManager::SetBuffers(
     scoped_ptr<base::SharedMemory> shm,
     bool enqueue_all_buffers) {
   DCHECK(shm);
-  DCHECK(!shm_);
   DCHECK_GT(number_of_buffers, 0);
   DCHECK_GT(buffer_size,
             static_cast<int32_t>(sizeof(MediaStreamBuffer::Header)));
@@ -45,6 +44,8 @@ bool MediaStreamBufferManager::SetBuffers(
   if (!shm_->Map(size))
     return false;
 
+  buffer_queue_.clear();
+  buffers_.clear();
   uint8_t* p = reinterpret_cast<uint8_t*>(shm_->memory());
   for (int32_t i = 0; i < number_of_buffers; ++i) {
     if (enqueue_all_buffers)