Blink uses access checks to be sure that objects from one context doesn't access objects in another. Heap profiler uses current context to call this checks, we need to be sure that current context is empty to allow heap profiler collect all objects without crash.

BUG=chromium:661223
R=alph@chromium.org,ulan@chromium.org

Review-Url: https://codereview.chromium.org/2669393002
Cr-Commit-Position: refs/heads/master@{#42939}