media: make the buffer_id in stream_buffer_manager consistent

The buffer_id is passed through Mojo as uint64, so we should refer to
the buffer_id throughout the code consistently as uint64_t.

BUG=832772
TBR=wuchengli

Change-Id: Ib6f260c4242e8c68510903cefcc997bf7a6bbd4d
Reviewed-on: https://chromium-review.googlesource.com/1073213Reviewed-by: Ricky Liang <jcliang@chromium.org>
Commit-Queue: Ricky Liang <jcliang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#561854}

media/capture/video/chromeos/stream_buffer_manager.cc

@@ -239,7 +239,7 @@ void StreamBufferManager::SetCaptureMetadata(cros::mojom::CameraMetadataTag tag,
 uint64_t StreamBufferManager::GetBufferIpcId(StreamType stream_type,
                                              size_t index) {
   uint64_t id = 0;
-  id |= static_cast<int64_t>(stream_type) << 32;
+  id |= static_cast<uint64_t>(stream_type) << 32;
   id |= index;
   return id;
 }
@@ -284,7 +284,7 @@ void StreamBufferManager::RegisterBuffer(StreamType stream_type) {
     return;
   }
 
-  size_t buffer_id = stream_context_[stream_type]->free_buffers.front();
+  uint64_t buffer_id = stream_context_[stream_type]->free_buffers.front();
   stream_context_[stream_type]->free_buffers.pop();
   const gfx::GpuMemoryBuffer* buffer =
       stream_context_[stream_type]->buffers[GetBufferIndex(buffer_id)].get();

media/capture/video/chromeos/stream_buffer_manager.h

@@ -235,10 +235,10 @@ class CAPTURE_EXPORT StreamBufferManager final
     std::vector<std::unique_ptr<gfx::GpuMemoryBuffer>> buffers;
     // The free buffers of this stream.  The queue stores indices into the
     // |buffers| vector.
-    std::queue<size_t> free_buffers;
+    std::queue<uint64_t> free_buffers;
     // The buffers that are registered to the HAL, which can be used as the
     // output buffers for capture requests.
-    std::queue<size_t> registered_buffers;
+    std::queue<uint64_t> registered_buffers;
     // The pointers to the pending capture results that have unsubmitted result
     // buffers.
     std::map<uint32_t, CaptureResult*> capture_results_with_buffer;