Delay signaling Shader cache is available until loading is complete.

content/browser/gpu/shader_disk_cache.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/gpu/shader_disk_cache.h"
 
 #include "base/threading/thread_checker.h"
 #include "content/browser/gpu/gpu_process_host.h"
 #include "content/public/browser/browser_thread.h"
 #include "net/base/io_buffer.h"
@@ skipping 555 matching lines @@
     return net::OK;
   available_callback_ = callback;
   return net::ERR_IO_PENDING;
 }
 
 void ShaderDiskCache::CacheCreatedCallback(int rv) {
   if (rv != net::OK) {
     LOG(ERROR) << "Shader Cache Creation failed: " << rv;
     return;
   }
-  cache_available_ = true;
-
   helper_ = new ShaderDiskReadHelper(AsWeakPtr(), host_id_);
   helper_->LoadCache();
-
-  if (!available_callback_.is_null()) {
-    available_callback_.Run(net::OK);
-    available_callback_.Reset();
-  }
 }
 
 void ShaderDiskCache::EntryComplete(void* entry) {
   entry_map_.erase(entry);
 
   if (entry_map_.empty() && !cache_complete_callback_.is_null())
     cache_complete_callback_.Run(net::OK);
 }
 
 void ShaderDiskCache::ReadComplete() {
   helper_ = NULL;
+
+  /* The cache is considered available after we have finished reading any

[apatrick_chromium, 2013/04/08 18:03:05]

nit: use // style comment rather than /* */

[dsinclair, 2013/04/09 22:52:02]

Done.

+   * of the old cache values off disk. This prevents a potential race where we
+   * are reading from disk and execute a cache clear at the same time. */
+  cache_available_ = true;
+  if (!available_callback_.is_null()) {
+    available_callback_.Run(net::OK);
+    available_callback_.Reset();
+  }
 }
 
 int ShaderDiskCache::SetCacheCompleteCallback(
     const net::CompletionCallback& callback) {
   if (entry_map_.empty()) {
     return net::OK;
   }
   cache_complete_callback_ = callback;
   return net::ERR_IO_PENDING;
 }
 
 }  // namespace content