Only destroy GPUTracer if the pointer is not empty.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 2d6425cc5d3e156b560154c592ed9431f5ce9e9f..3abe199f534969cce6c0ed433f9a0d7f3c4ca10c 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -3756,8 +3756,10 @@ void GLES2DecoderImpl::Destroy(bool have_context) {
   async_pixel_transfer_manager_.reset();
 
   // Destroy the GPU Tracer which may own some in process GPU Timings.
-  gpu_tracer_->Destroy(have_context);
-  gpu_tracer_ = NULL;
+  if (gpu_tracer_) {
+    gpu_tracer_->Destroy(have_context);
+    gpu_tracer_.reset();
+  }
 
   if (group_.get()) {
     framebuffer_manager()->RemoveObserver(this);