Clean up unused variable macros.

We might want UNUSED_ASSERTION as a special case but the unused trace
variable macro was being abused in places.

BUG=angleproject:1290

Change-Id: I5f9252b3ff0484d2e859b9fcf68d5d060b28f1fc
Reviewed-on: https://chromium-review.googlesource.com/324290
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Tested-by: Jamie Madill <jmadill@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>
diff --git a/src/common/BitSetIterator_unittest.cpp b/src/common/BitSetIterator_unittest.cpp
index 10fd3be..e965f2c 100644
--- a/src/common/BitSetIterator_unittest.cpp
+++ b/src/common/BitSetIterator_unittest.cpp
@@ -55,7 +55,7 @@
     for (unsigned long bit : IterateBitSet(mStateBits))
     {
         sawBit = true;
-        UNUSED_TRACE_VARIABLE(bit);
+        UNUSED_VARIABLE(bit);
     }
     EXPECT_FALSE(sawBit);
 }