Move GetNewTabCSS() caching off the startup path.

chrome/browser/ui/webui/theme_source.cc

Index: chrome/browser/ui/webui/theme_source.cc
diff --git a/chrome/browser/ui/webui/theme_source.cc b/chrome/browser/ui/webui/theme_source.cc
index 8e5de32c452c9535570c46d3c463ab3d632b134e..4234c4cf97971684fa5336e6b85b4177671c83c4 100644
--- a/chrome/browser/ui/webui/theme_source.cc
+++ b/chrome/browser/ui/webui/theme_source.cc
@@ -62,18 +62,22 @@ void ProcessResourceOnUIThread(int resource_id,
       scale, data);
 }
 
+base::RefCountedMemory* GetNewTabCSSOnUIThread(Profile* profile) {

[Evan Stade, 2016/10/03 20:16:59]

nit: style guide says NewTabCssOnUiThread

[Alexei Svitkine (slow), 2016/10/03 21:02:45]

Done - changed the other function in this file too for consistency.

+  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->GetOriginalProfile()) {
-  // NB: it's important that this is |profile| and not |profile_|.
-  NTPResourceCache::WindowType win_type =
-      NTPResourceCache::GetWindowType(profile, nullptr);
-  css_bytes_ =
-      NTPResourceCacheFactory::GetForProfile(profile)->GetNewTabCSS(win_type);
+    : profile_(profile),
+      original_profile_(profile->GetOriginalProfile()) {

[Evan Stade, 2016/10/03 20:16:59]

why not just inline profile_->GetOriginalProfile where it's needed?

[Alexei Svitkine (slow), 2016/10/03 21:02:45]

Done.

 }
 
 ThemeSource::~ThemeSource() {
@@ -95,7 +99,11 @@ void ThemeSource::StartDataRequest(
 
   if (IsNewTabCssPath(parsed_path)) {
     DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
-    callback.Run(css_bytes_.get());
+    // 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);
     return;
   }
 
@@ -175,12 +183,6 @@ base::MessageLoop* ThemeSource::MessageLoopForRequestPath(
       content::URLDataSource::MessageLoopForRequestPath(path) : nullptr;
 }
 
-bool ThemeSource::ShouldReplaceExistingSource() const {
-  // We currently get the css_bytes_ in the ThemeSource constructor, so we need
-  // to recreate the source itself when a theme changes.
-  return true;
-}
-
 bool ThemeSource::ShouldServiceRequest(const net::URLRequest* request) const {
   return request->url().SchemeIs(chrome::kChromeSearchScheme) ?
       InstantIOContext::ShouldServiceRequest(request) :
@@ -198,7 +200,7 @@ void ThemeSource::SendThemeBitmap(
   if (BrowserThemePack::IsPersistentImageID(resource_id)) {
     DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
     scoped_refptr<base::RefCountedMemory> image_data(
-        ThemeService::GetThemeProviderForProfile(profile_).GetRawData(
+        ThemeService::GetThemeProviderForProfile(original_profile_).GetRawData(
             resource_id, scale_factor));
     callback.Run(image_data.get());
   } else {
@@ -216,7 +218,7 @@ void ThemeSource::SendThemeImage(
   if (BrowserThemePack::IsPersistentImageID(resource_id)) {
     DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
     const ui::ThemeProvider& tp =
-        ThemeService::GetThemeProviderForProfile(profile_);
+        ThemeService::GetThemeProviderForProfile(original_profile_);
     ProcessImageOnUIThread(*tp.GetImageSkiaNamed(resource_id), scale, data);
     callback.Run(data.get());
   } else {