Allow DrawingBuffer to present to a bitmap.

public/platform/WebExternalTextureLayerClient.h

Index: public/platform/WebExternalTextureLayerClient.h
diff --git a/public/platform/WebExternalTextureLayerClient.h b/public/platform/WebExternalTextureLayerClient.h
index 4829600c21f94fd14262fd417331b98c55995be2..105a8bad77bd1b36905fc18398bce7140f01bb6d 100644
--- a/public/platform/WebExternalTextureLayerClient.h
+++ b/public/platform/WebExternalTextureLayerClient.h
@@ -32,6 +32,7 @@
 namespace WebKit {
 
 class WebGraphicsContext3D;
+class WebExternalBitmap;
 struct WebExternalTextureMailbox;
 
 class WebTextureUpdater {
@@ -49,7 +50,10 @@ public:
 
     // Returns true and provides a mailbox if a new frame is available.
     // Returns false if no new data is available and the old mailbox is to be reused.
-    virtual bool prepareMailbox(WebExternalTextureMailbox*) = 0;
+    virtual bool prepareMailbox(WebExternalTextureMailbox*, WebExternalBitmap*) = 0;
+
+    // OBSOLETE.

[Ken Russell (switch to Gerrit), 2013/07/02 11:22:12]

Could you please add a FIXME about removing it, pointing to this bug?

[jbauman, 2013/07/02 19:43:32]

Ok, done.

+    virtual bool prepareMailbox(WebExternalTextureMailbox* mailbox) { return prepareMailbox(mailbox, 0); }
 
     // Notifies the client when a mailbox is no longer in use by the compositor and provides
     // a sync point to wait on before the mailbox could be consumes again by the client.