[Favicon] Add new fallback icon rendering flow.

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 "chrome/browser/search/instant_io_context.h"
+#include "chrome/common/favicon/fallback_icon_url_parser.h"
+#include "chrome/common/url_constants.h"
+#include "net/url_request/url_request.h"
+#include "ui/gfx/favicon_size.h"
+
+FallbackIconSource::FallbackIconSource() {
+}
+
+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 = chrome::ParseFallbackIconPath(path, &parsed);
+  if (!success) {
+    SendDefaultResponse(callback);
+    return;
+  }
+
+  GURL url(parsed.url);
+  std::vector<unsigned char> bitmap_data =
+      fallback_icon_service_.RenderFallbackIconBitmap(
+          url, parsed.size_in_pixels, parsed.style);
+  callback.Run(base::RefCountedBytes::TakeVector(&bitmap_data));
+}
+
+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::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));
+}