Add ref-count on RenderViewHost for each new RenderFrameProxyHost.

This CL is a reland of https://codereview.chromium.org/1150793002/ with improved version of the test.

BUG=357747

Review URL: https://codereview.chromium.org/1151393003

Cr-Commit-Position: refs/heads/master@{#331221}
8 files changed