[Blob] Dependencies for blob storage testing

Source/platform/exported/WebThreadSafeData.cpp

Index: Source/platform/exported/WebThreadSafeData.cpp
diff --git a/Source/platform/exported/WebThreadSafeData.cpp b/Source/platform/exported/WebThreadSafeData.cpp
index 3341eaf423c73dd608fe7a3da9e5945c4aba7bc2..8ac5fd86aed045878f4f58930326f2bed3d9f47c 100644
--- a/Source/platform/exported/WebThreadSafeData.cpp
+++ b/Source/platform/exported/WebThreadSafeData.cpp
@@ -45,6 +45,12 @@ void WebThreadSafeData::assign(const WebThreadSafeData& other)
     m_private = other.m_private;
 }
 
+void WebThreadSafeData::assign(const char* data, size_t length)
+{
+    m_private = RawData::create().leakRef();
+    m_private->mutableData()->append(data, length);
+}
+
 size_t WebThreadSafeData::size() const
 {
     if (m_private.isNull())