A part of split CL to remove -Wno-enum-compare-switch flag

I will remove -Wno-enum-compare-switch flag to block incorrect enum type comparison.
To enable the warning let me fix the current codebase.

This CL is a part of effort.
https://chromium-review.googlesource.com/c/chromium/src/+/1286016

This CL was uploaded by git cl split.

R=raymes@chromium.org

Bug: 753973
Change-Id: If4e27fa4d1977a57080090c5a2275de64cee626f
Reviewed-on: https://chromium-review.googlesource.com/c/1288155
Commit-Queue: Takuto Ikuta <tikuta@chromium.org>
Reviewed-by: Raymes Khoury <raymes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#601064}

ppapi/shared_impl/private/ppb_char_set_shared.cc

@@ -113,15 +113,15 @@ PP_Bool PPB_CharSet_Shared::UTF16ToCharSet(
 
   // Setup our error handler.
   switch (on_error) {
-    case PP_CHARSET_CONVERSIONERROR_FAIL:
+    case PP_CHARSET_TRUSTED_CONVERSIONERROR_FAIL:
       ucnv_setFromUCallBack(converter, UCNV_FROM_U_CALLBACK_STOP, 0,
                             NULL, NULL, &status);
       break;
-    case PP_CHARSET_CONVERSIONERROR_SKIP:
+    case PP_CHARSET_TRUSTED_CONVERSIONERROR_SKIP:
       ucnv_setFromUCallBack(converter, UCNV_FROM_U_CALLBACK_SKIP, 0,
                             NULL, NULL, &status);
       break;
-    case PP_CHARSET_CONVERSIONERROR_SUBSTITUTE: {
+    case PP_CHARSET_TRUSTED_CONVERSIONERROR_SUBSTITUTE: {
       // ICU sets the substitution char for some character sets (like latin1)
       // to be the ASCII "substitution character" (26). We want to use '?'
       // instead for backwards-compat with Windows behavior.