gpu_process_launch_causes => content/common

This is used to establish the channel and has content-speciifc concepts.
This doesn't seem to belong to content/common/gpu as per piman@'s suggestion.

BUG=596290
CQ_INCLUDE_TRYBOTS=tryserver.chromium.win:win_optional_gpu_tests_rel

Review URL: https://codereview.chromium.org/1825183002

Cr-Commit-Position: refs/heads/master@{#382724}
16 files changed