Replace the index mapping of wallpaper picker UI and hard coded wallpaper index in C++

chrome/browser/ui/webui/options2/chromeos/wallpaper_thumbnail_source2.cc

Index: chrome/browser/ui/webui/options2/chromeos/wallpaper_thumbnail_source2.cc
diff --git a/chrome/browser/ui/webui/options2/chromeos/wallpaper_thumbnail_source2.cc b/chrome/browser/ui/webui/options2/chromeos/wallpaper_thumbnail_source2.cc
new file mode 100644
index 0000000000000000000000000000000000000000..225e8b58b4ea57574e949a231f767ea548b774c7
--- /dev/null
+++ b/chrome/browser/ui/webui/options2/chromeos/wallpaper_thumbnail_source2.cc
@@ -0,0 +1,93 @@
+// Copyright (c) 2011 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/options2/chromeos/wallpaper_thumbnail_source2.h"
+
+#include "ash/desktop_background/desktop_background_resources.h"
+#include "base/memory/singleton.h"
+#include "base/string_number_conversions.h"
+#include "base/string_piece.h"
+#include "base/string_util.h"
+#include "base/stringprintf.h"
+#include "base/threading/thread_restrictions.h"
+#include "chrome/browser/io_thread.h"
+#include "chrome/browser/ui/webui/chrome_url_data_manager.h"
+#include "chrome/common/url_constants.h"
+#include "content/public/browser/browser_thread.h"
+#include "grit/ui_resources.h"
+#include "net/base/mime_util.h"
+#include "ui/base/resource/resource_bundle.h"
+#include "ui/gfx/codec/png_codec.h"
+
+namespace chromeos {
+namespace options2 {
+
+namespace {
+
+const char kDefaultWallpaperPrefix[] = "default_";
+
+// Parse an integer from |path| and save it to |index|. For example, deafult_20
+// will set |index| to 20.
+// |path| and |index| must not be NULL.
+bool ParseIndexFromPath(const std::string& path, int* index) {
+  // TODO(bshe): We should probably save a string instead of index for
+  // extensibility. Remove this function when we migrate to string preference.
+  DCHECK(index);
+  if (!StartsWithASCII(path, kDefaultWallpaperPrefix, false))
+    return false;
+  return base::StringToInt(base::StringPiece(path.begin() +
+      strlen(kDefaultWallpaperPrefix), path.end()), index);
+}
+
+// Convert |path| to corresponding IDR. Return -1 if the path is invalid.
+// |path| must not be NULL.
+int PathToIDR(const std::string& path) {
+  int idr = -1;
+  int index = ash::GetInvalidWallpaperIndex();
+  if (ParseIndexFromPath(path, &index))
+    idr = ash::GetWallpaperInfo(index).thumb_id;
+  return idr;
+}
+
+}  // namespace
+
+std::string GetDefaultWallpaperThumbnailURL(int index) {
+  return StringPrintf("%s%s%d", chrome::kChromeUIWallpaperThumbnailURL,
+                      kDefaultWallpaperPrefix, index);
+}
+
+bool IsDefaultWallpaperURL(const std::string url, int* wallpaper_index) {
+  DCHECK(wallpaper_index);
+  *wallpaper_index = ash::GetInvalidWallpaperIndex();
+  if (!StartsWithASCII(url, chrome::kChromeUIWallpaperThumbnailURL, false))
+      return false;
+  std::string sub_path = url.substr(strlen(
+      chrome::kChromeUIWallpaperThumbnailURL));
+  return ParseIndexFromPath(sub_path, wallpaper_index);
+}
+
+WallpaperThumbnailSource::WallpaperThumbnailSource()
+    : DataSource(chrome::kChromeUIWallpaperThumbnailHost, NULL) {
+}
+
+WallpaperThumbnailSource::~WallpaperThumbnailSource() {
+}
+
+void WallpaperThumbnailSource::StartDataRequest(const std::string& path,
+                                                bool is_incognito,
+                                                int request_id) {
+  int idr = PathToIDR(path);
+  if (idr != -1) {
+    DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::IO));
+    const ResourceBundle& rb = ResourceBundle::GetSharedInstance();
+    SendResponse(request_id, rb.LoadDataResourceBytes(idr));
+  }
+}
+
+std::string WallpaperThumbnailSource::GetMimeType(const std::string&) const {
+  return "images/png";
+}
+
+}  // namespace options2
+}  // namespace chromeos