Add gamepad data fetcher for Linux

content/content_browser.gypi

Index: content/content_browser.gypi
diff --git a/content/content_browser.gypi b/content/content_browser.gypi
index 49526ea704e557d40df3fea300b8ab611a49a369..51358555f94f5f551f56b3bf319f4c85df99dbfa 100644
--- a/content/content_browser.gypi
+++ b/content/content_browser.gypi
@@ -213,14 +213,18 @@
     'browser/font_list_async.cc',
     'browser/font_list_async.h',
     'browser/gamepad/data_fetcher.h',
-    'browser/gamepad/data_fetcher_mac.mm',
+    'browser/gamepad/data_fetcher_linux.cc',
+    'browser/gamepad/data_fetcher_linux.h',
     'browser/gamepad/data_fetcher_mac.h',
+    'browser/gamepad/data_fetcher_mac.mm',
     'browser/gamepad/data_fetcher_win.cc',
     'browser/gamepad/data_fetcher_win.h',
     'browser/gamepad/gamepad_provider.cc',
     'browser/gamepad/gamepad_provider.h',
     'browser/gamepad/gamepad_service.cc',
     'browser/gamepad/gamepad_service.h',
+    'browser/gamepad/gamepad_standard_mappings_linux.cc',
+    'browser/gamepad/gamepad_standard_mappings_linux.h',
     'browser/geolocation/access_token_store.cc',
     'browser/geolocation/access_token_store.h',
     'browser/geolocation/arbitrator_dependency_factory.cc',
@@ -698,6 +702,11 @@
         }],
       ],
     }],
+    ['OS=="linux"', {
+      'include_dirs': [
+        '../third_party/libudev',
+      ],
+    }],
     ['OS=="linux" and toolkit_uses_gtk==0', {
       'dependencies': [
         '../build/linux/system.gyp:dbus',