Avoid touching ResourceBundle fonts from non-UI thread

content/browser/webui/shared_resources_data_source.cc

 // Copyright (c) 2012 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/webui/shared_resources_data_source.h"
 
 #include <stddef.h>
 
 #include "base/containers/hash_tables.h"
 #include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
+#include "content/public/browser/browser_thread.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/url_constants.h"
 #include "ui/base/layout.h"
 #include "ui/base/webui/web_ui_util.h"
 #include "ui/resources/grit/webui_resources.h"
 #include "ui/resources/grit/webui_resources_map.h"
 
 #if defined(OS_WIN)
 #include "base/strings/utf_string_conversions.h"
 #endif
@@ skipping 64 matching lines @@
   auto it = resources_map.find(path);
   int idr = (it != resources_map.end()) ? it->second : -1;
   DCHECK_NE(-1, idr) << " path: " << path;
   scoped_refptr<base::RefCountedMemory> bytes;
 
   if (idr == IDR_WEBUI_CSS_TEXT_DEFAULTS) {
     std::string css = webui::GetWebUiCssTextDefaults();
     bytes = base::RefCountedString::TakeString(&css);
   } else if (idr == IDR_WEBUI_CSS_TEXT_DEFAULTS_MD) {
     std::string css = webui::GetWebUiCssTextDefaultsMd();
     bytes = base::RefCountedString::TakeString(&css);

[Dan Beam, 2017/02/23 00:27:56]

these are the calls that actually ask for a gfx::Font().  just move these 2
calls (GetWebUiCssTextDefaults*()) on the UI thread.

   } else {
     bytes = GetContentClient()->GetDataResourceBytes(idr);
   }
 
   callback.Run(bytes.get());
 }
 
 std::string SharedResourcesDataSource::GetMimeType(
     const std::string& path) const {
   if (path.empty())
@@ skipping 31 matching lines @@
   if (extension == "woff2")
     return "application/font-woff2";
 
   NOTREACHED() << path;
   return "text/plain";
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 SharedResourcesDataSource::TaskRunnerForRequestPath(
     const std::string& path) const {
+  // Use UI thread to load CSS since its construction touches non-thread-safe
+  // gfx::Font names in ui::ResourceBundle.
+  if (GetMimeType(path) == "text/css")
+    return BrowserThread::GetTaskRunnerForThread(BrowserThread::UI);

[Dan Beam, 2017/02/23 00:27:56]

sorry, don't do this

[Dan Beam, 2017/02/23 00:32:26]

and by that i mean, push all text/css to the UI thread.

also, should we just call the super?

... SharedResourcesDataSource::TaskRunnerForRequestPath(...) const {
  const ResourcesMap& resources = GetResourcesMap();
  auto it = resources.find(path);
  if (it != resources.end() &&
      (it->second == IDR_WEBUI_CSS_TEXT_DEFAULTS ||
       it->second == IDR_WEBUI_CSS_TEXT_DEFAULTS_MD)) {
    return URLDataSource::TaskRunnerForRequestPath(path);
  }
  return nullptr;
}

[tzik, 2017/02/23 00:58:19]

Updated.

[tzik, 2017/02/23 00:58:19]

Hmm, I think it's unclear from this code that the super class returns the UI
thread task runner. Can we take it from BrowserThread?

[Dan Beam, 2017/02/23 02:11:30]

i'm fine with either

   return nullptr;
 }
 
 std::string
 SharedResourcesDataSource::GetAccessControlAllowOriginForOrigin(
     const std::string& origin) const {
   // For now we give access only for "chrome://*" origins.
   // According to CORS spec, Access-Control-Allow-Origin header doesn't support
   // wildcards, so we need to set its value explicitly by passing the |origin|
   // back.
   std::string allowed_origin_prefix = kChromeUIScheme;
   allowed_origin_prefix += "://";
   if (!base::StartsWith(origin, allowed_origin_prefix,
                         base::CompareCase::SENSITIVE)) {
     return "null";
   }
   return origin;
 }
 
 }  // namespace content