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

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index b652408781292dcabc393cb8919471f25ea4acb3..11afa202a4a48361f519d29225c13603e6567ec8 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -53,6 +53,7 @@
 #include "content/browser/gpu/gpu_data_manager_impl.h"
 #include "content/browser/gpu/gpu_process_host.h"
 #include "content/browser/gpu/gpu_process_host_ui_shim.h"
+#include "content/browser/gpu/shader_disk_cache.h"
 #include "content/browser/histogram_synchronizer.h"
 #include "content/browser/loader/resource_dispatcher_host_impl.h"
 #include "content/browser/loader_delegate_impl.h"
@@ -1227,6 +1228,13 @@ int BrowserMainLoop::BrowserThreadsStarted() {
   }
 #endif
 
+  // Initialize the GPU shader cache. This needs to be initialized before
+  // BrowserGpuChannelHostFactory below, since that depends on an initialized
+  // ShaderCacheFactory.
+  ShaderCacheFactory::InitInstance(
+      BrowserThread::GetTaskRunnerForThread(BrowserThread::IO),
+      BrowserThread::GetTaskRunnerForThread(BrowserThread::CACHE));
+
   bool always_uses_gpu = true;
   bool established_gpu_channel = false;
 #if defined(OS_ANDROID)