Add a use counter for creating processing instructions on HTML docs

third_party/WebKit/Source/core/dom/Document.cpp

Index: third_party/WebKit/Source/core/dom/Document.cpp
diff --git a/third_party/WebKit/Source/core/dom/Document.cpp b/third_party/WebKit/Source/core/dom/Document.cpp
index bab0b6ed7e0395e7c5b2cd33274ab8919e608690..685a2737cfabe75c890847b3331872ea4ace87ce 100644
--- a/third_party/WebKit/Source/core/dom/Document.cpp
+++ b/third_party/WebKit/Source/core/dom/Document.cpp
@@ -997,6 +997,10 @@ ProcessingInstruction* Document::createProcessingInstruction(
         "The data provided ('" + data + "') contains '?>'.");
     return nullptr;
   }
+  if (isHTMLDocument()) {
+    UseCounter::count(*this,
+                      UseCounter::HTMLDocumentCreateProcessingInstruction);
+  }
   return ProcessingInstruction::create(*this, target, data);
 }