ExtensionFunctionDispatcher should use base::Process::Current() if single process
mode.

Since #323179, ExtensionFunctionDispatcher has used
base::Process::DeprecatedGetProcessFromHandle to callback:
https://chromium.googlesource.com/chromium/src/+/f8d789c4558c7575f4d388d44730d18fdf157
72c
However, base::Process::DeprecatedGetProcessFromHandle(handle) assumes
 |handle| is not current process handle. The assumption brakes if single process mode
 thus chrome can't start with the '--single-process' flag.

BUG=477001

Review URL: https://codereview.chromium.org/1113343002

Cr-Commit-Position: refs/heads/master@{#328923}
1 file changed