
Add support to goog.net.XhrIo for the new responseType mechanism.

This mechanism allows XHRs to be read into local Blobs, which can then be saved
to the filesystem for offline use.

R=nicksantos
DELTA=129  (127 added, 0 deleted, 2 changed)


Revision created by MOE tool push_codebase.
MOE_MIGRATION=180


ajukraine/closure-compiler,ajukraine/closure-compiler