Add use counters for Fetch API.

Source/modules/fetch/Body.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "modules/fetch/Body.h"
 
 #include "bindings/core/v8/ExceptionState.h"
 #include "bindings/core/v8/ScriptPromiseResolver.h"
 #include "bindings/core/v8/ScriptState.h"
 #include "bindings/core/v8/V8ArrayBuffer.h"
 #include "bindings/core/v8/V8ThrowException.h"
 #include "core/dom/DOMArrayBuffer.h"
 #include "core/fileapi/Blob.h"
 #include "core/fileapi/FileReaderLoader.h"
 #include "core/fileapi/FileReaderLoaderClient.h"
+#include "core/frame/UseCounter.h"
 #include "core/streams/UnderlyingSource.h"
 #include "modules/fetch/BodyStreamBuffer.h"
 
 namespace blink {
 
 class Body::BlobHandleReceiver final : public BodyStreamBuffer::BlobHandleCreatorClient {
 public:
     explicit BlobHandleReceiver(Body* body)
         : m_body(body)
     {
@@ skipping 203 matching lines @@
     return readAsync(scriptState, ResponseAsJSON);
 }
 
 ScriptPromise Body::text(ScriptState* scriptState)
 {
     return readAsync(scriptState, ResponseAsText);
 }
 
 ReadableStream* Body::body()
 {
+    UseCounter::count(executionContext(), UseCounter::FetchBodyStream);
     if (!m_streamAccessed) {
         m_streamAccessed = true;
         if (m_stream->isPulling()) {
             // The stream has been pulling, but the source ignored the
             // instruction because it didn't know the user wanted to use the
             // ReadableStream interface. Now it knows the user does, so have
             // the source start pulling.
             m_streamSource->pullSource();
         }
     }
@@ skipping 180 matching lines @@
 
 void Body::didBlobHandleReceiveError(PassRefPtrWillBeRawPtr<DOMException> exception)
 {
     if (!m_resolver)
         return;
     m_resolver->reject(exception);
     m_resolver.clear();
 }
 
 } // namespace blink