[Fallback Icons] Refactor FallbackIconService to be a BrowserContext-level singleton

chrome/browser/ui/webui/fallback_icon_source.cc

 // Copyright 2015 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/fallback_icon_source.h"
 
-#include <string>
 #include <vector>
 
 #include "base/memory/ref_counted_memory.h"
 #include "chrome/browser/search/instant_io_context.h"
 #include "chrome/common/favicon/fallback_icon_url_parser.h"
 #include "chrome/common/url_constants.h"
-#include "grit/platform_locale_settings.h"
+#include "components/favicon/core/fallback_icon_service.h"
+#include "components/keyed_service/core/service_access_type.h"
 #include "net/url_request/url_request.h"
-#include "ui/base/l10n/l10n_util.h"
 #include "ui/gfx/favicon_size.h"
 #include "url/gurl.h"
 
-FallbackIconSource::FallbackIconSource() {
-  std::vector<std::string> font_list;
-#if defined(OS_CHROMEOS)
-  font_list.push_back("Noto Sans");
-#elif defined(OS_IOS)
-  font_list.push_back("Helvetica Neue");
-#else
-  font_list.push_back(l10n_util::GetStringUTF8(IDS_SANS_SERIF_FONT_FAMILY));
-#endif
-  fallback_icon_service_.reset(new FallbackIconService(font_list));
+FallbackIconSource::FallbackIconSource(
+    FallbackIconService* fallback_icon_service)
+    : fallback_icon_service_(fallback_icon_service) {
 }
 
 FallbackIconSource::~FallbackIconSource() {
 }
 
 std::string FallbackIconSource::GetSource() const {
   return chrome::kChromeUIFallbackIconHost;
 }
 
 void FallbackIconSource::StartDataRequest(
     const std::string& path,
     int render_process_id,
     int render_frame_id,
     const content::URLDataSource::GotDataCallback& callback) {
   chrome::ParsedFallbackIconPath parsed;
   bool success = parsed.Parse(path);
   if (!success) {
     SendDefaultResponse(callback);
     return;
   }
+
   GURL url(parsed.url_string());
   if (url.is_empty() || !url.is_valid()) {
     SendDefaultResponse(callback);
     return;
   }
-  std::vector<unsigned char> bitmap_data =
-      fallback_icon_service_->RenderFallbackIconBitmap(
-          url, parsed.size_in_pixels(), parsed.style());
-  callback.Run(base::RefCountedBytes::TakeVector(&bitmap_data));
+
+  SendFallbackIconHelper(
+      url, parsed.size_in_pixels(), parsed.style(), callback);
 }
 
 std::string FallbackIconSource::GetMimeType(const std::string&) const {
   // We need to explicitly return a mime type, otherwise if the user tries to
   // drag the image they get no extension.
   return "image/png";
 }
 
 bool FallbackIconSource::ShouldReplaceExistingSource() const {
   // Leave the existing DataSource in place, otherwise we'll drop any pending
   // requests on the floor.
   return false;
 }
 
 bool FallbackIconSource::ShouldServiceRequest(
     const net::URLRequest* request) const {
   if (request->url().SchemeIs(chrome::kChromeSearchScheme))
     return InstantIOContext::ShouldServiceRequest(request);
   return URLDataSource::ShouldServiceRequest(request);
 }
 
+void FallbackIconSource::SendFallbackIconHelper(
+    const GURL& url,
+    int size_in_pixels,
+    const favicon_base::FallbackIconStyle& style,
+    const content::URLDataSource::GotDataCallback& callback) {
+  if (!fallback_icon_service_) {
+    SendNotFoundResponse(callback);
+    return;
+  }
+  std::vector<unsigned char> bitmap_data =
+      fallback_icon_service_->RenderFallbackIconBitmap(
+          url, size_in_pixels, style);
+  callback.Run(base::RefCountedBytes::TakeVector(&bitmap_data));
+}
+
 void FallbackIconSource::SendDefaultResponse(
     const content::URLDataSource::GotDataCallback& callback) {
-  std::vector<unsigned char> bitmap_data =
-      fallback_icon_service_->RenderFallbackIconBitmap(
-          GURL(), gfx::kFaviconSize, favicon_base::FallbackIconStyle());
-  callback.Run(base::RefCountedBytes::TakeVector(&bitmap_data));
+  favicon_base::FallbackIconStyle default_style;
+  SendFallbackIconHelper(GURL(), gfx::kFaviconSize, default_style, callback);
 }
+
+void FallbackIconSource::SendNotFoundResponse(
+    const content::URLDataSource::GotDataCallback& callback) {
+  callback.Run(nullptr);
+}