Ping watchdog thread during GpuChannel destruction

gpu/command_buffer/service/memory_program_cache_unittest.cc

Index: gpu/command_buffer/service/memory_program_cache_unittest.cc
diff --git a/gpu/command_buffer/service/memory_program_cache_unittest.cc b/gpu/command_buffer/service/memory_program_cache_unittest.cc
index a4a78c6299078af5dd2595aaa5fc8fb84dce4e07..a28b79d9f22dc232990da266c791a93e8c53ee6c 100644
--- a/gpu/command_buffer/service/memory_program_cache_unittest.cc
+++ b/gpu/command_buffer/service/memory_program_cache_unittest.cc
@@ -77,10 +77,10 @@ class MemoryProgramCacheTest : public GpuServiceTest {
 
   MemoryProgramCacheTest()
       : cache_(new MemoryProgramCache(kCacheSizeBytes, kDisableGpuDiskCache)),
-        vertex_shader_(NULL),
-        fragment_shader_(NULL),
-        shader_cache_count_(0) {
-  }
+        shader_manager_(nullptr),
+        vertex_shader_(nullptr),
+        fragment_shader_(nullptr),
+        shader_cache_count_(0) {}
   ~MemoryProgramCacheTest() override { shader_manager_.Destroy(false); }
 
   void ShaderCacheCb(const std::string& key, const std::string& shader) {