Make blink::WritableStream a pure virtual class

In preparation for adding the native implementation, rename the existing
implementation to blink::WritableStreamWrapper and make
blink::WritableStream be a virtual base class for it. When the native
implementation is added, Create() methods and other places that need to
work with the real type will check a runtime flag.


Change-Id: I97c6b4e5b1461b0b3b0092773db60644b3711b5f
Reviewed-by: Yutaka Hirano <>
Commit-Queue: Adam Rice <>
Cr-Commit-Position: refs/heads/master@{#622843}
8 files changed