Implement ChromeOS mime type extension mappings.

net/base/platform_mime_util_linux.cc

Index: net/base/platform_mime_util_linux.cc
diff --git a/net/base/platform_mime_util_linux.cc b/net/base/platform_mime_util_linux.cc
index ff7f79b1549fe81313df94c66e572f0a5b739926..96b9bfa076d7ae9b0159ec748ca901c8472e7a02 100644
--- a/net/base/platform_mime_util_linux.cc
+++ b/net/base/platform_mime_util_linux.cc
@@ -11,6 +11,8 @@
 
 #if defined(OS_ANDROID)
 #include "net/android/network_library.h"
+#elif defined(OS_CHROMEOS)
+#include "net/base/mime_extension_chromeos.h"
 #else
 #include "base/nix/mime_util_xdg.h"
 #endif
@@ -22,6 +24,12 @@ bool PlatformMimeUtil::GetPlatformMimeTypeFromExtension(
     const base::FilePath::StringType& ext, std::string* result) const {
   return android::GetMimeTypeFromExtension(ext, result);
 }
+#elif defined(OS_CHROMEOS)
+bool PlatformMimeUtil::GetPlatformMimeTypeFromExtension(
+    const base::FilePath::StringType& ext,
+    std::string* result) const {
+  return chromeos::GetPlatformMimeTypeFromExtension(ext, result);
+}
 #else
 bool PlatformMimeUtil::GetPlatformMimeTypeFromExtension(
     const base::FilePath::StringType& ext, std::string* result) const {