gpu shader cache: Clarify lifetime/ownership/threadiness of objects.

content/browser/renderer_host/render_process_host_impl.cc

Index: content/browser/renderer_host/render_process_host_impl.cc
diff --git a/content/browser/renderer_host/render_process_host_impl.cc b/content/browser/renderer_host/render_process_host_impl.cc
index 036c2d7e65021284f38fca1ad00bc5717cad6e10..cd16442cedd8847a2cea31118990c4955fc0d20b 100644
--- a/content/browser/renderer_host/render_process_host_impl.cc
+++ b/content/browser/renderer_host/render_process_host_impl.cc
@@ -256,11 +256,13 @@ const base::FilePath::CharType kAecDumpFileNameAddition[] =
 #endif
 
 void CacheShaderInfo(int32_t id, base::FilePath path) {
-  ShaderCacheFactory::GetInstance()->SetCacheInfo(id, path);
+  if (ShaderCacheFactory::GetInstance())
+    ShaderCacheFactory::GetInstance()->SetCacheInfo(id, path);
 }
 
 void RemoveShaderInfo(int32_t id) {
-  ShaderCacheFactory::GetInstance()->RemoveCacheInfo(id);
+  if (ShaderCacheFactory::GetInstance())
+    ShaderCacheFactory::GetInstance()->RemoveCacheInfo(id);
 }
 
 net::URLRequestContext* GetRequestContext(