Remove a bunch of NPAPI quirks and related support code

content/child/BUILD.gn

Index: content/child/BUILD.gn
diff --git a/content/child/BUILD.gn b/content/child/BUILD.gn
index d6993efe0235c951c17949488519ee41935a6c6d..ee79f1810f83643d094a9e98c91b17a0a670d3fa 100644
--- a/content/child/BUILD.gn
+++ b/content/child/BUILD.gn
@@ -93,11 +93,7 @@ source_set("child") {
         "npapi/webplugin_delegate_impl_mac.mm",
       ]
     } else if (is_win) {
-      sources -= [
-        "npapi/webplugin_delegate_impl_win.cc",
-        "npapi/webplugin_ime_win.cc",
-        "npapi/webplugin_ime_win.h",
-      ]
+      sources -= [ "npapi/webplugin_delegate_impl_win.cc" ]
     } else if (is_android) {
       sources -= [ "npapi/webplugin_delegate_impl_android.cc" ]
     }