GpuChannelHost: allocate route IDs on the client (renderer) side.

This avoids a timing-sensitive bug where the pattern of non-Host-allocated
route IDs are in conflict with non-Host-initiated-first-IPC.

BUG=360276
TEST=trybot and manual testing.
[email protected], [email protected], [email protected]

Review URL: https://codereview.chromium.org/227433010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@262553 0039d316-1c4b-4281-b951-d872f2087c98
31 files changed