[Blob] Dependencies for blob storage testing

public/platform/WebThreadSafeData.h

Index: public/platform/WebThreadSafeData.h
diff --git a/public/platform/WebThreadSafeData.h b/public/platform/WebThreadSafeData.h
index 2b9abac517bc0b52f230265e301f9d91c7040bed..e0e03326949906f1884cd8f5a718bef8bf4a1485 100644
--- a/public/platform/WebThreadSafeData.h
+++ b/public/platform/WebThreadSafeData.h
@@ -50,6 +50,9 @@ public:
     ~WebThreadSafeData() { reset(); }
 
     BLINK_PLATFORM_EXPORT void assign(const WebThreadSafeData&);
+    // For testing use only.

[pdr., 2015/06/02 20:26:16]

Other than two instances in WebLayer.h, I don't see other cases where we've
exposed things in platform for testing. How are similar apis tested today?

+    BLINK_PLATFORM_EXPORT void assign(const char* data, size_t length);
+
     BLINK_PLATFORM_EXPORT void reset();
 
     BLINK_PLATFORM_EXPORT size_t size() const;