Call Client methods synchronously in FetchDataLoader if the first read is Done or error

Source/modules/fetch/FetchDataLoader.cpp

Index: Source/modules/fetch/FetchDataLoader.cpp
diff --git a/Source/modules/fetch/FetchDataLoader.cpp b/Source/modules/fetch/FetchDataLoader.cpp
index fde86106545c3854ea79c3e7bbaad8bcc5b38489..244d48e624a4158907f2e2246fdfc365723fbb4d 100644
--- a/Source/modules/fetch/FetchDataLoader.cpp
+++ b/Source/modules/fetch/FetchDataLoader.cpp
@@ -52,6 +52,7 @@ private:
         // We read data from |m_reader| and create a new blob.
         m_blobData = BlobData::create();
         m_blobData->setContentType(m_mimeType);
+        didGetReadable();
     }
 
     void didGetReadable() override
@@ -136,6 +137,7 @@ protected:
         m_client = client;
         m_rawData = adoptPtr(new ArrayBufferBuilder());
         m_reader = handle->obtainReader(this);
+        didGetReadable();
     }
 
     void didGetReadable() override
@@ -234,6 +236,7 @@ protected:
         ASSERT(!m_reader);
         m_client = client;
         m_reader = handle->obtainReader(this);
+        didGetReadable();
     }
 
     void didGetReadable() override