Move RTCSessionDescriptionRequest to platform/

BUG=297477

Review URL: https://codereview.chromium.org/60083012

git-svn-id: svn://svn.chromium.org/blink/trunk@161633 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Refactor TimelineOverview to make squeezing impl-side frames easier

This makes some of TimelineFrameOverview members easier to reuse
by removing side effects and dependency on the class state.

BUG=305863

Review URL: https://codereview.chromium.org/59983002

git-svn-id: svn://svn.chromium.org/blink/trunk@161634 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Create SearchController instance per each Searchable.

R=pfeldman

Review URL: https://codereview.chromium.org/55973002

git-svn-id: svn://svn.chromium.org/blink/trunk@161635 bbb929c8-8fbe-4397-9dbb-9b2b20218538