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

content/browser/storage_partition_impl_unittest.cc

Index: content/browser/storage_partition_impl_unittest.cc
diff --git a/content/browser/storage_partition_impl_unittest.cc b/content/browser/storage_partition_impl_unittest.cc
index 26ec5d432265267f1f85c3f2099359f8e98f8ec7..dc3ee844829085d15e802addb8a393837ca6a223 100644
--- a/content/browser/storage_partition_impl_unittest.cc
+++ b/content/browser/storage_partition_impl_unittest.cc
@@ -601,6 +601,9 @@ class StoragePartitionShaderClearTest : public testing::Test {
   StoragePartitionShaderClearTest()
       : thread_bundle_(content::TestBrowserThreadBundle::IO_MAINLOOP),
         browser_context_(new TestBrowserContext()) {
+    ShaderCacheFactory::InitInstance(
+        base::ThreadTaskRunnerHandle::Get(),
+        BrowserThread::GetTaskRunnerForThread(BrowserThread::CACHE));
     ShaderCacheFactory::GetInstance()->SetCacheInfo(
         kDefaultClientId,
         BrowserContext::GetDefaultStoragePartition(