Add UMA for header values in XHR's setRequestHeader() checked against RFC 7230

third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp

Index: third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp
diff --git a/third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp b/third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp
index 7e5e8ef292b0cdce0a6fcd28d3c14b48ba903465..a349e01044173ddc66cf26e3ed9ab188147b0806 100644
--- a/third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp
+++ b/third_party/WebKit/Source/core/xmlhttprequest/XMLHttpRequest.cpp
@@ -70,6 +70,7 @@
 #include "platform/network/ParsedContentType.h"
 #include "platform/network/ResourceError.h"
 #include "platform/network/ResourceRequest.h"
+#include "public/platform/Platform.h"
 #include "public/platform/WebURLRequest.h"
 #include "wtf/Assertions.h"
 #include "wtf/StdLibExtras.h"
@@ -131,6 +132,13 @@ void logConsoleError(ExecutionContext* context, const String& message)
     context->addConsoleMessage(ConsoleMessage::create(JSMessageSource, ErrorMessageLevel, message));
 }
 
+enum HeaderValueCategoryByRFC7230 {
+    HeaderValueInvalid,
+    HeaderValueAffectedByNormalization,
+    HeaderValueValid,
+    HeaderValueCategoryByRFC7230End
+};
+
 } // namespace
 
 class XMLHttpRequest::BlobLoader final : public GarbageCollectedFinalized<XMLHttpRequest::BlobLoader>, public FileReaderLoaderClient {
@@ -1174,10 +1182,6 @@ void XMLHttpRequest::setRequestHeader(const AtomicString& name, const AtomicStri
         return;
     }
 
-    // Show deprecation warnings and count occurrences of such deprecated header values.
-    if (!value.isEmpty() && !isValidHTTPFieldContentRFC7230(value))
-        UseCounter::countDeprecation(executionContext(), UseCounter::HeaderValueNotMatchingRFC7230);
-
     // No script (privileged or not) can set unsafe headers.
     if (FetchUtils::isForbiddenHeaderName(name)) {
         logConsoleError(executionContext(), "Refused to set unsafe header \"" + name + "\"");
@@ -1189,9 +1193,31 @@ void XMLHttpRequest::setRequestHeader(const AtomicString& name, const AtomicStri
 
 void XMLHttpRequest::setRequestHeaderInternal(const AtomicString& name, const AtomicString& value)
 {
+    HeaderValueCategoryByRFC7230 headerValueCategory = HeaderValueValid;
+
     HTTPHeaderMap::AddResult result = m_requestHeaders.add(name, value);
-    if (!result.isNewEntry)
-        result.storedValue->value = result.storedValue->value + ", " + value;
+    if (!result.isNewEntry) {
+        AtomicString newValue = result.storedValue->value + ", " + value;
+
+        // Without normalization at XHR level here, the actual header value
+        // sent to the network is |newValue| with leading/trailing whitespaces
+        // stripped (i.e. |normalizeHeaderValue(newValue)|).
+        // With normalization at XHR level here as the spec requires, the
+        // actual header value sent to the network is |normalizedNewValue|.
+        // If these two are different, introducing normalization here affects
+        // the header value sent to the network.
+        String normalizedNewValue = FetchUtils::normalizeHeaderValue(result.storedValue->value) + ", " + FetchUtils::normalizeHeaderValue(value);
+        if (FetchUtils::normalizeHeaderValue(newValue) != normalizedNewValue)
+            headerValueCategory = HeaderValueAffectedByNormalization;
+
+        result.storedValue->value = newValue;
+    }
+
+    String normalizedValue = FetchUtils::normalizeHeaderValue(value);
+    if (!normalizedValue.isEmpty() && !isValidHTTPFieldContentRFC7230(normalizedValue))
+        headerValueCategory = HeaderValueInvalid;
+
+    Platform::current()->histogramEnumeration("Blink.XHR.setRequestHeader.HeaderValueCategoryInRFC7230", headerValueCategory, HeaderValueCategoryByRFC7230End);
 }
 
 const AtomicString& XMLHttpRequest::getRequestHeader(const AtomicString& name) const