Fork methods on BlobRegistry for Stream and Blob

We decided to keep Stream and Blob separate for a while to avoid conflict
between two big efforts (Blob identifier redesign by michaeln and Stream
addition by tyoshino).

Chromium side change is here:
https://codereview.chromium.org/15817013/

BUG=169957

Review URL: https://chromiumcodereview.appspot.com/20745003

git-svn-id: svn://svn.chromium.org/blink/trunk@155429 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Make timeline event bars ordered by their start time.

Previously bars of timeline events those durations was smaller than a minimal
width where expanded to the min width, and their left edge was moved to the
left by width/2. That led to some events appeared as they occurred earlier
than an event above it.

BUG=267459
R=caseq@chromium.org

Review URL: https://codereview.chromium.org/21596002

git-svn-id: svn://svn.chromium.org/blink/trunk@155430 bbb929c8-8fbe-4397-9dbb-9b2b20218538