[PresentationAPI] Make sendBlobData() pure virtual in WebPresentationClient.

public/platform/modules/presentation/WebPresentationClient.h

Index: public/platform/modules/presentation/WebPresentationClient.h
diff --git a/public/platform/modules/presentation/WebPresentationClient.h b/public/platform/modules/presentation/WebPresentationClient.h
index a60ce32b0c16c19db37dcb634e5bff7ff6b34f7d..82d740d2c1aa21e0e0fea211f2e5989fa4564e85 100644
--- a/public/platform/modules/presentation/WebPresentationClient.h
+++ b/public/platform/modules/presentation/WebPresentationClient.h
@@ -49,11 +49,7 @@ public:
 
     // Called when the frame requests to send Blob data to an existing session.
     // Embedder copies the |data| and the ownership is not transferred.
-    virtual void sendBlobData(const WebString& presentationUrl, const WebString& presentationId, const uint8_t* data, size_t length)
-    {
-        // TODO(s.singapati): Make this method pure virtual once Chromium has the implementation.
-        BLINK_ASSERT_NOT_REACHED();
-    }
+    virtual void sendBlobData(const WebString& presentationUrl, const WebString& presentationId, const uint8_t* data, size_t length) = 0;
 
     // Called when the frame requests to close an existing session.
     virtual void closeSession(const WebString& url, const WebString& presentationId) = 0;