DevTools: Fix slowness of searching after moving lineAt method to utilities.js

R=pfeldman, apavlov

Review URL: https://codereview.chromium.org/153663006

git-svn-id: svn://svn.chromium.org/blink/trunk@166401 bbb929c8-8fbe-4397-9dbb-9b2b20218538
V8PerContextDataHolder should know the world associated with the V8PerContextDataHolder

This is one of incremental steps to clean up code about worlds and contexts.

- Currently V8PerContextDataHolder understands its associated world only if the world is an isolated world. This CL makes V8PerContextDataHolder understand its associated world always.

- This CL adds V8PerIsolateData::m_isMainThread and removes V8PerIsolateData::m_workerDOMDataStore.

BUG=339800

Review URL: https://codereview.chromium.org/146693019

git-svn-id: svn://svn.chromium.org/blink/trunk@166402 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: follow up to r166401, added 'new' to call String constructor, not cast.

TBR=apavlov

Review URL: https://codereview.chromium.org/153063004

git-svn-id: svn://svn.chromium.org/blink/trunk@166403 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Devtools: Code which manages worker's frontend was moved into the separate class

BUG=

Review URL: https://codereview.chromium.org/152523003

git-svn-id: svn://svn.chromium.org/blink/trunk@166404 bbb929c8-8fbe-4397-9dbb-9b2b20218538
DevTools: Fix bad method call when clicked on empty retainers grid header

R=yurys@chromium.org

Review URL: https://codereview.chromium.org/150603005

git-svn-id: svn://svn.chromium.org/blink/trunk@166405 bbb929c8-8fbe-4397-9dbb-9b2b20218538