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/bind.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 37 matching lines @@
 
   return result;
 }
 
 const ResourcesMap& GetResourcesMap() {
   // This pointer will be intentionally leaked on shutdown.
   static const ResourcesMap* resources_map = CreateResourcesMap();
   return *resources_map;
 }
 
+scoped_refptr<base::RefCountedMemory> GetResourceBytesOnUIThread(int idr) {
+  if (idr == IDR_WEBUI_CSS_TEXT_DEFAULTS) {
+    std::string css = webui::GetWebUiCssTextDefaults();
+    return base::RefCountedString::TakeString(&css);
+  }
+
+  if (idr == IDR_WEBUI_CSS_TEXT_DEFAULTS_MD) {
+    std::string css = webui::GetWebUiCssTextDefaultsMd();
+    return base::RefCountedString::TakeString(&css);
+  }
+
+  return GetContentClient()->GetDataResourceBytes(idr);
+}
+
 }  // namespace
 
 SharedResourcesDataSource::SharedResourcesDataSource() {
 }
 
 SharedResourcesDataSource::~SharedResourcesDataSource() {
 }
 
 std::string SharedResourcesDataSource::GetSource() const {
   return kChromeUIResourcesHost;
 }
 
 void SharedResourcesDataSource::StartDataRequest(
     const std::string& path,
     const ResourceRequestInfo::WebContentsGetter& wc_getter,
     const URLDataSource::GotDataCallback& callback) {
   const ResourcesMap& resources_map = GetResourcesMap();
   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);
-  } else {
-    bytes = GetContentClient()->GetDataResourceBytes(idr);
-  }
-
-  callback.Run(bytes.get());
+  BrowserThread::PostTaskAndReplyWithResult(
+      BrowserThread::UI, FROM_HERE,
+      base::Bind(&GetResourceBytesOnUIThread, idr), callback);
 }
 
 std::string SharedResourcesDataSource::GetMimeType(
     const std::string& path) const {
   if (path.empty())
     return "text/html";
 
 #if defined(OS_WIN)
   base::FilePath file(base::UTF8ToWide(path));
   std::string extension = base::WideToUTF8(file.FinalExtension());
@@ skipping 26 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 {
   return nullptr;

[Dan Beam, 2017/02/22 22:56:10]

i think you should only return nullptr when GetMime(path) !=
"application/font-woff2"

[tzik, 2017/02/22 23:47:02]

Sounds nice! Updated.
Let me use "text/css" since the problematic resource is a CSS.

 }
 
 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