DevTools: [CanvasProfiler] Fix crash on Linux Debug.

Do not modify HashMap/HashTable during it's iteration.

BUG=261079
R=yurys@chromium.org

Review URL: https://chromiumcodereview.appspot.com/19510004

git-svn-id: svn://svn.chromium.org/blink/trunk@154394 bbb929c8-8fbe-4397-9dbb-9b2b20218538