Do not attempt to open a channel to a plugin in Plugin Data Remover if there are no plugins available.

BUG=485886

Review URL: https://codereview.chromium.org/1144353003

Cr-Commit-Position: refs/heads/master@{#331168}
PluginDataRemoverImpl::~PluginDataRemoverImpl() {
}

PluginDataRemoverImpl::~PluginDataRemoverImpl() {
}
