Make current class filter value apply to snapshot when switching between views

This fixes following problem: take two snapshots go to comparison view and type something that doesn't match any name in the class filter field, no switch to the summary view, clear the filter and switch back to the comparison view - it is empty despite the filter input is also empty.

BUG=None

Review URL: https://codereview.chromium.org/225483002

git-svn-id: svn://svn.chromium.org/blink/trunk@170867 bbb929c8-8fbe-4397-9dbb-9b2b20218538