Change the variable name "buffer_state_bit" into "client_state_mask".

Reasons:
1. This variable is not refering to a property of the buffer. It refers
to a client of the buffer.
2. The original "buffer_state_bit" of a producer/consumer is actually
the client state bit mask for both buffer_state and fence_state in
shared memory. Thus, "buffer_state_bit" does not make sense for the
fence state.
3. In the future, Every clients takes up two bits in the buffer_state.
For simpler bit manipulation, there will be a future change making the
client_state_bits two bits as well. Please refer to ag/5236978 for an
early look at the future bit manipulation. Thus, this change replaces
"bit" with "mask".

Test: build
Bug: 112007999
Change-Id: I72f59ab9491bd2f135da068f578195fbf5e6c2b6
diff --git a/services/vr/bufferhubd/buffer_channel.cpp b/services/vr/bufferhubd/buffer_channel.cpp
index ee85746..d5e6dfb 100644
--- a/services/vr/bufferhubd/buffer_channel.cpp
+++ b/services/vr/bufferhubd/buffer_channel.cpp
@@ -18,7 +18,7 @@
     : BufferHubChannel(service, buffer_id, channel_id, kDetachedBufferType),
       buffer_node_(
           std::make_shared<BufferNode>(std::move(buffer), user_metadata_size)) {
-  buffer_state_bit_ = buffer_node_->AddNewActiveClientsBitToMask();
+  client_state_mask_ = buffer_node_->AddNewActiveClientsBitToMask();
 }
 
 BufferChannel::BufferChannel(BufferHubService* service, int buffer_id,
@@ -28,7 +28,7 @@
     : BufferHubChannel(service, buffer_id, buffer_id, kDetachedBufferType),
       buffer_node_(std::make_shared<BufferNode>(
           width, height, layer_count, format, usage, user_metadata_size)) {
-  buffer_state_bit_ = buffer_node_->AddNewActiveClientsBitToMask();
+  client_state_mask_ = buffer_node_->AddNewActiveClientsBitToMask();
 }
 
 BufferChannel::BufferChannel(BufferHubService* service, int buffer_id,
@@ -36,8 +36,8 @@
                              std::shared_ptr<BufferNode> buffer_node)
     : BufferHubChannel(service, buffer_id, channel_id, kDetachedBufferType),
       buffer_node_(buffer_node) {
-  buffer_state_bit_ = buffer_node_->AddNewActiveClientsBitToMask();
-  if (buffer_state_bit_ == 0ULL) {
+  client_state_mask_ = buffer_node_->AddNewActiveClientsBitToMask();
+  if (client_state_mask_ == 0ULL) {
     ALOGE("BufferChannel::BufferChannel: %s", strerror(errno));
     buffer_node_ = nullptr;
   }
@@ -46,8 +46,8 @@
 BufferChannel::~BufferChannel() {
   ALOGD_IF(TRACE, "BufferChannel::~BufferChannel: channel_id=%d buffer_id=%d.",
            channel_id(), buffer_id());
-  if (buffer_state_bit_ != 0ULL) {
-    buffer_node_->RemoveClientsBitFromMask(buffer_state_bit_);
+  if (client_state_mask_ != 0ULL) {
+    buffer_node_->RemoveClientsBitFromMask(client_state_mask_);
   }
   Hangup();
 }
@@ -93,7 +93,7 @@
       /*buffer_handle=*/buffer_node_->buffer().handle(),
       /*metadata_handle=*/buffer_node_->metadata().ashmem_handle().Borrow(),
       /*id=*/buffer_id(),
-      /*buffer_state_bit=*/buffer_state_bit_,
+      /*client_state_mask=*/client_state_mask_,
       /*metadata_size=*/buffer_node_->metadata().metadata_size(),
       /*width=*/buffer_node_->buffer().width(),
       /*height=*/buffer_node_->buffer().height(),