[HBD] Fix the misleading no-fallback placeholder message in BLOCK mode.
Previously, if the user had the BLOCK Content Setting (either from
Policy or just from user setting), the no-fallback placeholder for
HTML5 By Default would still say "Click to enable Flash".
This was misleading because that would not work. This updates the BLOCK
no-fallback placeholder to say "Flash is blocked" and "Flash is blocked
by enterprise policy" (if blocked by policy).
BUG=666774
Review-Url: https://codereview.chromium.org/2511263003
Cr-Commit-Position: refs/heads/master@{#435289}
6 files changed
