Merge GenMailboxCHROMIUM into ProduceTextureDirectCHROMIUM

ProduceTextureDirectCHROMIUM is always called after GenMailboxCHROMIUM
(or equivalently gpu::Mailbox::Generate()), so merge both calls into a
single one. This isn't intended to change any behavior.

Note, TakeFrontBuffer still takes an explicitly generated gpu::Mailbox.

Bug: 847674
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel;master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_layout_tests_slimming_paint_v2
Change-Id: I7227ddffba6291c1efe3ed589bfbc6166f3319fe
Reviewed-on: https://chromium-review.googlesource.com/1089695
Commit-Queue: Antoine Labour <[email protected]>
Reviewed-by: Jeremy Roman <[email protected]>
Reviewed-by: Jonathan Backer <[email protected]>
Reviewed-by: Justin Novosad <[email protected]>
Reviewed-by: David Reveman <[email protected]>
Reviewed-by: Frank Liberato <[email protected]>
Reviewed-by: Klaus Weidner <[email protected]>
Cr-Commit-Position: refs/heads/master@{#566633}
70 files changed