Figure out the MIME type of shared WebUI resources more efficiently

content/browser/webui/shared_resources_data_source.cc

Index: content/browser/webui/shared_resources_data_source.cc
diff --git a/content/browser/webui/shared_resources_data_source.cc b/content/browser/webui/shared_resources_data_source.cc
index d30e03f6c2ef21922a2c9020c969aea22fa9007a..aa1289c279e19cd9f3786f02f63971e66a4ca971 100644
--- a/content/browser/webui/shared_resources_data_source.cc
+++ b/content/browser/webui/shared_resources_data_source.cc
@@ -7,19 +7,22 @@
 #include <stddef.h>
 
 #include "base/containers/hash_tables.h"
+#include "base/files/file_path.h"
 #include "base/logging.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/strings/string_piece.h"
 #include "base/strings/string_util.h"
-#include "base/threading/thread_restrictions.h"
 #include "content/public/common/content_client.h"
 #include "content/public/common/url_constants.h"
-#include "net/base/mime_util.h"
 #include "ui/base/layout.h"
 #include "ui/base/webui/web_ui_util.h"
 #include "ui/resources/grit/webui_resources.h"
 #include "ui/resources/grit/webui_resources_map.h"
 
+#if defined(OS_WIN)
+#include "base/strings/utf_string_conversions.h"
+#endif
+
 namespace content {
 
 namespace {
@@ -104,13 +107,45 @@ void SharedResourcesDataSource::StartDataRequest(
 
 std::string SharedResourcesDataSource::GetMimeType(
     const std::string& path) const {
-  // Requests should not block on the disk!  On POSIX this goes to disk.
-  // http://code.google.com/p/chromium/issues/detail?id=59849
+  if (path.empty())
+    return "text/html";
+
+#if defined(OS_WIN)
+  base::FilePath file(base::UTF8ToWide(path));
+  std::string extension = base::WideToUTF8(file.FinalExtension()).substr(1);
+#else
+  base::FilePath file(path);
+  std::string extension = file.FinalExtension().substr(1);
+#endif
+
+  if (extension == "html")
+    return "text/html";
+
+  if (extension == "css")
+    return "text/css";
+
+  if (extension == "js")
+    return "application/javascript";
+
+  if (extension == "png")
+    return "image/png";
 
-  base::ThreadRestrictions::ScopedAllowIO allow_io;
-  std::string mime_type;
-  net::GetMimeTypeFromFile(base::FilePath().AppendASCII(path), &mime_type);
-  return mime_type;
+  if (extension == "gif")
+    return "image/gif";
+
+  if (extension == "svg")
+    return "image/svg+xml";
+
+  if (extension == "woff2")
+    return "application/font-woff2";
+
+  CHECK(false) << path;
+  return "text/plain";
+}
+
+base::MessageLoop* SharedResourcesDataSource::MessageLoopForRequestPath(
+    const std::string& path) const {
+  return nullptr;
 }
 
 std::string