Refactor download image-MIME-type-detection code.

chrome/browser/download/download_item_model.cc

Index: chrome/browser/download/download_item_model.cc
diff --git a/chrome/browser/download/download_item_model.cc b/chrome/browser/download/download_item_model.cc
index 95eb7b78040f583635d8244c8e17da461217906c..51ff68dd164c68d76a968a693b490020031937d6 100644
--- a/chrome/browser/download/download_item_model.cc
+++ b/chrome/browser/download/download_item_model.cc
@@ -23,9 +23,11 @@
 #include "chrome/common/safe_browsing/download_file_types.pb.h"
 #include "chrome/grit/chromium_strings.h"
 #include "chrome/grit/generated_resources.h"
+#include "components/mime_util/mime_util.h"
 #include "content/public/browser/download_danger_type.h"
 #include "content/public/browser/download_interrupt_reasons.h"
 #include "content/public/browser/download_item.h"
+#include "net/base/mime_util.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/l10n/time_format.h"
 #include "ui/base/text/bytes_formatting.h"
@@ -513,6 +515,23 @@ bool DownloadItemModel::IsMalicious() const {
   return false;
 }
 
+bool DownloadItemModel::HasSupportedImageMimeType() const {
+  if (mime_util::IsSupportedImageMimeType(download_->GetMimeType())) {
+    return true;
+  }
+
+  std::string mime;
+  base::FilePath::StringType extension_with_dot =
+      download_->GetTargetFilePath().FinalExtension();
+  if (!extension_with_dot.empty() && net::GetWellKnownMimeTypeFromExtension(
+                                         extension_with_dot.substr(1), &mime) &&
+      mime_util::IsSupportedImageMimeType(mime)) {
+    return true;
+  }
+
+  return false;
+}
+
 bool DownloadItemModel::ShouldAllowDownloadFeedback() const {
 #if defined(FULL_SAFE_BROWSING)
   if (!IsDangerous())