Allow ParsedContentType to reject multiple definitions of the same parameter

third_party/WebKit/Source/platform/network/ParsedContentType.cpp

Index: third_party/WebKit/Source/platform/network/ParsedContentType.cpp
diff --git a/third_party/WebKit/Source/platform/network/ParsedContentType.cpp b/third_party/WebKit/Source/platform/network/ParsedContentType.cpp
index fb288e72b75104017e639190c2c67bc29534f4fc..8490b843d0a6742e7df0692e3888837996709706 100644
--- a/third_party/WebKit/Source/platform/network/ParsedContentType.cpp
+++ b/third_party/WebKit/Source/platform/network/ParsedContentType.cpp
@@ -264,11 +264,15 @@ bool ParsedContentType::parse(const String& contentType) {
                << ", for '" << key.toString() << "').";
       return false;
     }
-    String keyString = key.toString();
     // As |key| is parsed as a token, it consists of ascii characters
     // and hence we don't need to care about non-ascii lowercasing.
-    DCHECK(keyString.containsOnlyASCII());
-    map.set(keyString.lower(), value);
+    DCHECK(key.toString().containsOnlyASCII());
+    String keyString = key.toString().lower();
+    if (m_mode == Mode::Strict && map.find(keyString) != map.end()) {
+      DVLOG(1) << "Parameter " << keyString << " is defined multiple times.";
+      return false;
+    }
+    map.set(keyString, value);
   }
   m_parameters = std::move(map);
   return true;