Measure impact of [SecureContext] on WebCrypto.

third_party/WebKit/Source/modules/crypto/SubtleCrypto.cpp

Index: third_party/WebKit/Source/modules/crypto/SubtleCrypto.cpp
diff --git a/third_party/WebKit/Source/modules/crypto/SubtleCrypto.cpp b/third_party/WebKit/Source/modules/crypto/SubtleCrypto.cpp
index 5c3e3e3c646c425170f9d2f3af1279805a2c5ee4..9d8c75e5deb39fce411ec48c6b6b663ad104e615 100644
--- a/third_party/WebKit/Source/modules/crypto/SubtleCrypto.cpp
+++ b/third_party/WebKit/Source/modules/crypto/SubtleCrypto.cpp
@@ -35,6 +35,7 @@
 #include "core/dom/DOMArrayBufferView.h"
 #include "core/dom/DOMArrayPiece.h"
 #include "core/dom/ExecutionContext.h"
+#include "core/frame/UseCounter.h"
 #include "modules/crypto/CryptoHistograms.h"
 #include "modules/crypto/CryptoKey.h"
 #include "modules/crypto/CryptoResultImpl.h"
@@ -65,6 +66,12 @@ static bool canAccessWebCrypto(ScriptState* scriptState, CryptoResult* result) {
     return false;
   }
 
+  if (!scriptState->getExecutionContext()->isSecureContext()) {
+    UseCounter::count(
+        scriptState->getExecutionContext(),
+        UseCounter::SubtleCryptoOnlyStrictSecureContextCheckFailed);
+  }
+
   return true;
 }