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/libs/ui/tests/BufferHubBuffer_test.cpp b/libs/ui/tests/BufferHubBuffer_test.cpp
index be06ad2..f0253b2 100644
--- a/libs/ui/tests/BufferHubBuffer_test.cpp
+++ b/libs/ui/tests/BufferHubBuffer_test.cpp
@@ -100,12 +100,12 @@
     // These two buffer instances are based on the same physical buffer under the
     // hood, so they should share the same id.
     EXPECT_EQ(id1, id2);
-    // We use buffer_state_bit() to tell those two instances apart.
-    EXPECT_NE(b1->buffer_state_bit(), b2->buffer_state_bit());
-    EXPECT_NE(b1->buffer_state_bit(), 0ULL);
-    EXPECT_NE(b2->buffer_state_bit(), 0ULL);
-    EXPECT_NE(b1->buffer_state_bit(), kProducerStateBit);
-    EXPECT_NE(b2->buffer_state_bit(), kProducerStateBit);
+    // We use client_state_mask() to tell those two instances apart.
+    EXPECT_NE(b1->client_state_mask(), b2->client_state_mask());
+    EXPECT_NE(b1->client_state_mask(), 0ULL);
+    EXPECT_NE(b2->client_state_mask(), 0ULL);
+    EXPECT_NE(b1->client_state_mask(), kProducerStateBit);
+    EXPECT_NE(b2->client_state_mask(), kProducerStateBit);
 
     // Both buffer instances should be in gained state.
     EXPECT_TRUE(IsBufferGained(b1->buffer_state()));