Added Destroy() functions for GPUTimer and GPUTracer/GPUTrace.

gpu/command_buffer/service/gpu_tracer_unittest.cc

Index: gpu/command_buffer/service/gpu_tracer_unittest.cc
diff --git a/gpu/command_buffer/service/gpu_tracer_unittest.cc b/gpu/command_buffer/service/gpu_tracer_unittest.cc
index 8aed1c67ce63470fa36e1fc5311be06feff9ac6c..2a6896ef9f4577d73bee19a26a894b45805c151a 100644
--- a/gpu/command_buffer/service/gpu_tracer_unittest.cc
+++ b/gpu/command_buffer/service/gpu_tracer_unittest.cc
@@ -228,6 +228,7 @@ class BaseGpuTest : public GpuServiceTest {
 
   void TearDown() override {
     outputter_ref_ = NULL;
+    gpu_timing_client_ = NULL;
 
     gl_fake_queries_.Reset();
     GpuServiceTest::TearDown();
@@ -374,6 +375,9 @@ class BaseGpuTraceTest : public BaseGpuTest {
     // Proces should output expected Trace results to MockOutputter
     trace->Process();
 
+    // Destroy trace after we are done.
+    trace->Destroy(true);
+
     outputter_ref_ = NULL;
   }
 };