Revert 155122 - Code to collect issue 97285 debugging info for crash reports.

Revert 155122 - Code to collect issue 97285 debugging info for crash reports.
[TPM is suspicious of Windows renderer crash rate.  Seems impossible,
but who knows?]

It is useful to record breakpad keys for debugging, which is not
applicable to multi-process bugs.  This adds infrastructure to allow
collection of information across processes.

Also, fix so that GetPluginChannelHost() can successfully fail without
crashing.

BUG=97285, 141055
Review URL: https://chromiumcodereview.appspot.com/10908078

TBR=shess@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=155240