Currently there are no crash handlers for uncaught java exceptions
in child processes. Add a chrome debug url to crash the GPU process
with an uncaught java exception to aid in testing this code path.

The plumbing is same as chrome://gpucrash, except everything is
behind OS_ANDROID guards. The actual implementation of throwing
the exception is in base.

BUG=680775
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_site_isolation

Review-Url: https://codereview.chromium.org/2664373002
Cr-Commit-Position: refs/heads/master@{#447908}