Unfork TextCodecICU.cpp. The upstream accepted my patch with some changes ...

third_party/WebKit/WebCore/platform/text/TextCodecICU.cpp

Index: third_party/WebKit/WebCore/platform/text/TextCodecICU.cpp
===================================================================
--- third_party/WebKit/WebCore/platform/text/TextCodecICU.cpp	(revision 6434)
+++ third_party/WebKit/WebCore/platform/text/TextCodecICU.cpp	(working copy)
@@ -110,17 +110,19 @@
                 continue;
         }
 
-        // Here, we used to alias GB2312 and GB2312-80 to GBK, but our copy
-        // of ICU treats GB2312/GB2312-80 as synonyms of GBK so that we
-        // don't need that any more.
+        // 1. Treat GB2312 encoding as GBK (its more modern superset), to match other browsers.
+        // 2. On the Web, GB2312 is encoded as EUC-CN or HZ, while ICU provides a native encoding
+        //    for encoding GB_2312-80 and several others. So, we need to override this behavior, too.
+        if (strcmp(standardName, "GB2312") == 0 || strcmp(standardName, "GB_2312-80") == 0)
+            standardName = "GBK";
         // Similarly, EUC-KR encodings all map to an extended version.
-        if (strcmp(standardName, "KSC_5601") == 0 || strcmp(standardName, "EUC-KR") == 0 || strcmp(standardName, "cp1363") == 0)
-            standardName = "windows-949-2000";
+        else if (strcmp(standardName, "KSC_5601") == 0 || strcmp(standardName, "EUC-KR") == 0 || strcmp(standardName, "cp1363") == 0)
+            standardName = "windows-949";
         // And so on.
         else if (strcasecmp(standardName, "iso-8859-9") == 0) // This name is returned in different case by ICU 3.2 and 3.6.
             standardName = "windows-1254";
         else if (strcmp(standardName, "TIS-620") == 0)
-            standardName = "windows-874-2000";
+            standardName = "windows-874";
 
         registrar(standardName, standardName);
 
@@ -136,30 +138,35 @@
             }
     }
 
-    // We used to map macroman and xmacroman to macintosh, but 
-    // we don't need them any more because they're added to our
-    // local copy of ICU.
+    // Additional aliases.
+    // These are present in modern versions of ICU, but not in ICU 3.2 (shipped with Mac OS X 10.4).
+    registrar("macroman", "macintosh");
+    registrar("maccyrillic", "x-mac-cyrillic");
 
     // Additional aliases that historically were present in the encoding
     // table in WebKit on Macintosh that don't seem to be present in ICU.
     // Perhaps we can prove these are not used on the web and remove them.
     // Or perhaps we can get them added to ICU.
+    registrar("xmacroman", "macintosh");
+    registrar("xmacukrainian", "x-mac-cyrillic");
     registrar("cnbig5", "Big5");
-    registrar("cngb", "EUC-CN");
+    registrar("xxbig5", "Big5");
+    registrar("cngb", "GBK");
+    registrar("csgb231280", "GBK");
+    registrar("xeuccn", "GBK");
+    registrar("xgbk", "GBK");
     registrar("csISO88598I", "ISO_8859-8-I");
-    registrar("csgb231280", "EUC-CN");
-    registrar("dos720", "cp864");
-    registrar("dos874", "TIS-620");
-    registrar("jis7", "ISO-2022-JP");
     registrar("koi", "KOI8-R");
     registrar("logical", "ISO-8859-8-I");
     registrar("unicode11utf8", "UTF-8");
     registrar("unicode20utf8", "UTF-8");
+    registrar("xunicode20utf8", "UTF-8");
     registrar("visual", "ISO-8859-8");
     registrar("winarabic", "windows-1256");
     registrar("winbaltic", "windows-1257");
     registrar("wincyrillic", "windows-1251");
-    registrar("iso885911", "windows874-2000");
+    registrar("iso885911", "windows-874");
+    registrar("dos874", "windows-874");
     registrar("wingreek", "windows-1253");
     registrar("winhebrew", "windows-1255");
     registrar("winlatin2", "windows-1250");
@@ -168,16 +175,9 @@
     registrar("xcp1250", "windows-1250");
     registrar("xcp1251", "windows-1251");
     registrar("xeuc", "EUC-JP");
-    registrar("xeuccn", "EUC-CN");
-    registrar("xgbk", "EUC-CN");
-    registrar("xunicode20utf8", "UTF-8");
-    registrar("xwindows949", "windows-949-2000");
-    registrar("xxbig5", "Big5");
+    registrar("xwindows949", "windows-949");
+    registrar("xuhc", "windows-949");
 
-    // This alias is present in modern versions of ICU, but it has no standard name,
-    // so we give one to it manually. It is not present in ICU 3.2.
-    registrar("windows874", "windows874-2000");
-
     // These aliases are present in modern versions of ICU, but use different codecs, and have no standard names.
     // They are not present in ICU 3.2.
     registrar("dos720", "cp864");
@@ -482,4 +482,3 @@
 
 
 } // namespace WebCore
-