ThemeSource: simplify thread hopping for NTP CSS

chrome/browser/ui/webui/theme_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 "chrome/browser/ui/webui/theme_source.h"
 
 #include "base/memory/ref_counted_memory.h"
 #include "base/message_loop/message_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "chrome/browser/profiles/profile.h"
@@ skipping 44 matching lines @@
 
 void ProcessResourceOnUiThread(int resource_id,
                                float scale,
                                scoped_refptr<base::RefCountedBytes> data) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   ProcessImageOnUiThread(
       *ResourceBundle::GetSharedInstance().GetImageSkiaNamed(resource_id),
       scale, data);
 }
 
-base::RefCountedMemory* GetNewTabCSSOnUiThread(Profile* profile) {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-
-  NTPResourceCache::WindowType type =
-      NTPResourceCache::GetWindowType(profile, nullptr);
-  return NTPResourceCacheFactory::GetForProfile(profile)->GetNewTabCSS(type);
-}
-
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // ThemeSource, public:
 
 ThemeSource::ThemeSource(Profile* profile) : profile_(profile) {}
 
-ThemeSource::~ThemeSource() {
-}
+ThemeSource::~ThemeSource() = default;
 
 std::string ThemeSource::GetSource() const {
   return chrome::kChromeUIThemeHost;
 }
 
 void ThemeSource::StartDataRequest(
     const std::string& path,
     const content::ResourceRequestInfo::WebContentsGetter& wc_getter,
     const content::URLDataSource::GotDataCallback& callback) {
   // Default scale factor if not specified.
   float scale = 1.0f;
   std::string parsed_path;
   webui::ParsePathAndScale(GetThemeUrl(path), &parsed_path, &scale);
 
   if (IsNewTabCssPath(parsed_path)) {
-    DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
-    // NB: it's important that this is |profile_| and not |original_profile_|.
-    content::BrowserThread::PostTaskAndReplyWithResult(
-        content::BrowserThread::UI, FROM_HERE,
-        base::Bind(&GetNewTabCSSOnUiThread, profile_), callback);
+    DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+    NTPResourceCache::WindowType type =
+        NTPResourceCache::GetWindowType(profile_, /*render_host=*/nullptr);
+    NTPResourceCache* cache = NTPResourceCacheFactory::GetForProfile(profile_);
+    callback.Run(cache->GetNewTabCSS(type));
     return;
   }
 
   int resource_id = -1;
   if (parsed_path == "current-channel-logo") {
     switch (chrome::GetChannel()) {
 #if defined(GOOGLE_CHROME_BUILD)
       case version_info::Channel::CANARY:
         resource_id = IDR_PRODUCT_LOGO_32_CANARY;
         break;
@@ skipping 48 matching lines @@
   webui::ParsePathAndScale(GetThemeUrl(path), &parsed_path, nullptr);
   return IsNewTabCssPath(parsed_path) ? "text/css" : "image/png";
 }
 
 scoped_refptr<base::SingleThreadTaskRunner>
 ThemeSource::TaskRunnerForRequestPath(const std::string& path) const {
   std::string parsed_path;
   webui::ParsePathAndScale(GetThemeUrl(path), &parsed_path, nullptr);
 
   if (IsNewTabCssPath(parsed_path)) {
-    // We generated and cached this when we initialized the object.  We don't
-    // have to go back to the UI thread to send the data.
-    return nullptr;
+    // We'll get this data from the NTPResourceCache, which must be accessed on
+    // the UI thread.
+    return content::URLDataSource::TaskRunnerForRequestPath(path);
   }
 
   // If it's not a themeable image, we don't need to go to the UI thread.
   int resource_id = ResourcesUtil::GetThemeResourceId(parsed_path);
   return BrowserThemePack::IsPersistentImageID(resource_id)
              ? content::URLDataSource::TaskRunnerForRequestPath(path)
              : nullptr;
 }
 
 bool ThemeSource::AllowCaching() const {
@@ skipping 46 matching lines @@
   } else {
     DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
     // Fetching image data in ResourceBundle should happen on the UI thread. See
     // crbug.com/449277
     content::BrowserThread::PostTaskAndReply(
         content::BrowserThread::UI, FROM_HERE,
         base::BindOnce(&ProcessResourceOnUiThread, resource_id, scale, data),
         base::BindOnce(callback, data));
   }
 }