Add test name to benchmark report.

Explicit benchmark (unittest) name in the benchmark result record makes
it easier to read and/or automatically collect into benchmarks table.

Bug: 158517134
Test: build and run
Change-Id: I5c9de48c052d411a5facf09eaceaf613ae0667c9
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2236603
Auto-Submit: Michael Montvelishsky <mont@chromium.org>
Commit-Queue: Kenneth MacKay <kmackay@chromium.org>
Reviewed-by: Kenneth MacKay <kmackay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#776297}

chromecast/media/cma/backend/mixer/post_processors/post_processor_unittest.cc

@@ -245,7 +245,10 @@ void AudioProcessorBenchmark(AudioPostProcessor2* pp,
     pp->ProcessFrames(&data_in[i], kBufSizeFrames, 1.0, 0.0);
   }
   clock_t stop_clock = clock();
-  LOG(INFO) << "At " << sample_rate
+  const ::testing::TestInfo* const test_info =
+      ::testing::UnitTest::GetInstance()->current_test_info();
+  LOG(INFO) << test_info->test_suite_name() << "." << test_info->name()
+            << " At " << sample_rate
             << " frames per second CPU usage: " << std::defaultfloat
             << 100.0 * (stop_clock - start_clock) /
                    (CLOCKS_PER_SEC * effective_duration)